JPS5943793B2 - Anti-log conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-logarithmic conversion circuit that uses a semiconductor PN junction as an anti-logarithmic conversion element to convert an arithmetic level input signal into a corresponding geometric level output signal. In particular, the temperature-sensitive resistor for temperature compensation, which was indispensable to the anti-logarithmic converter, is completely unnecessary.

Most conventional antilogarithmic converters use PN junctions such as transistors and diodes as antilogarithmic conversion elements.

By the way, the voltage-current characteristic of a semiconductor PN junction is -
It is expressed as 1sexpqV(-).

However, Is is the reverse saturation current, KTk is Boltzmann's constant, and T
is the gelpin temperature, and q is the amount of electron charge.

That is, the PN junction has an inverse logarithm conversion element, but also has a change element due to temperature T. In particular, although the inverse saturation current 1s is small in absolute value, it changes almost exponentially with temperature changes. One of the pair of PN junctions is used for voltage-current antilogarithm conversion, and the other is used for canceling the inverse saturation current 1s, thereby eliminating fluctuations in antilogarithmic conversion characteristics due to temperature changes in the inverse saturation current 1s. However, since the temperature T in the above characteristic equation is in the exponential term, pairability cannot be compensated for.
For this reason, in conventional anti-logarithmic converters, the temperature T in the characteristic equation is canceled out using a temperature-sensitive resistor whose resistance value changes in direct proportion or inverse proportion to the temperature. The resistance coefficient of resistance is nonlinear with respect to temperature, and even if various combinations are tried, it is impossible to completely match the desired temperature compensation characteristics over a wide temperature range. Moreover, the resistance values and temperature coefficients of temperature-sensitive resistors vary widely, and even if it happens that one temperature can be compensated, it is not possible to completely compensate for the temperature of all of them when mass-produced. Furthermore, in order to achieve perfect temperature compensation, selecting a temperature-sensitive resistor element alone becomes expensive. Therefore, the conventional anti-logarithmic converter has to be expensive because it is very difficult to perfectly compensate for the temperature of the anti-logarithmic conversion characteristic including the variation. The present invention was made to eliminate the above-mentioned drawbacks, and it converts an input signal into an electrical signal (voltage or current) that changes in proportion to absolute temperature and is proportional to the input signal, and The present invention provides an anti-logarithmic conversion circuit that performs anti-logarithmic conversion on an input signal using an anti-logarithmic amplifier to obtain an anti-logarithmically converted output electric signal that is stable against temperature changes.

Examples thereof will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a temperature-sensitive electrical signal generator that uses a semiconductor PN junction as a temperature-sensitive element and generates an electrical signal that changes in proportion to the absolute temperature (TCK). The temperature-sensitive voltage generator 100 generates a voltage 8 that changes in proportion to the absolute temperature T, using a transistor as the temperature-sensitive voltage generator 100. Reference numeral 2 denotes an input signal conversion circuit, which receives an input signal and the output electric signal of the temperature-sensitive electric signal generator 1, and generates an electric signal that changes in proportion to the absolute temperature and is proportional to the input signal.

As will be described later, the input signals input to the input signal conversion circuit 2 include not only analog electrical signals such as analog voltage and current, but also digital signals expressed as discrete numerical values and mechanical signals such as keyboards for electronic musical instruments. It may also be switching selection information of a switch, furthermore, setting position information of a variable resistance resistor.

In the embodiment shown in FIG. 1, an analog multiplier 22 that multiplies analog voltages is used as the input signal conversion circuit 2, and a voltage VTO is outputted to an output terminal 21. 3 is an antilogarithmic amplifier using a semiconductor PN junction as an antilogarithmic conversion element, and the antilogarithmic conversion characteristic is not temperature compensated.

The antilogarithmic amplifier 3 receives the output voltage TO of the input signal conversion circuit 2.
is inverse logarithmically transformed to obtain current 1c=Aexp(BVTc/T
) is output. However, T is the absolute temperature (°K), A, B
represents a constant that does not depend on the absolute temperature T. In the embodiment shown in FIG. 1, the antilogarithmic amplifier 3 uses a transistor as an antilogarithmic conversion element. In addition, temperature-sensitive voltage generator 1
The transistor 00 and the transistor of the antilogarithmic amplifier 3 are at substantially the same temperature. Next, the operation of the embodiment shown in FIG. 1 will be briefly explained.

Since the output voltage (temperature sensitive voltage) T of the temperature sensitive voltage generator 100 is proportional to the absolute temperature, it is expressed as VT=KTT. However, KT is a proportionality constant that does not depend on temperature. When the input signal is given as input voltage IN, analog multiplier 2
Since the output voltage VTC of No. 2 is proportional to the product of the output voltage T of the temperature-sensitive voltage generator 100 and the input voltage IN, T
It is expressed as C=MVINVT=MKTVINT. However, M is a proportionality constant that does not depend on temperature. As mentioned above, the output current c of the antilogarithmic amplifier 3 is Ic=Aexp(BV
Tc/T). Therefore, the output current 1c is calculated by substituting VTC=MKTVINT into the above equation and calculating Ic=Aexp(B
MKTVINT/T)=Aexp(BMKTVIN), and the temperature T disappears.

Therefore, the output current is the inverse logarithmic transformation of the input voltage 1N. is stable against temperature changes. Next, the embodiment shown in FIG. 1 will be described in detail.

FIG. 1 shows a specific embodiment of the temperature-sensitive voltage generator 100. Al, A2 is a high input impedance differential amplifier, T
, l, T, and 2 are paired transistors having the same voltage-current characteristics, and 11 to 14 are resistors that are stable against temperature changes. The resistors that ground the non-inverting inputs of the differential amplifiers Al and A2 are intended to eliminate offsets caused by the input bias current 1B of the differential amplifiers A and A2, respectively. Also, capacitors 16 and 17 between the outputs and inverting inputs of the differential amplifiers Al and A2, and resistors 15 interposed between the output of the differential amplifier A2 and both emitters of the transistors T, l, T, and 2. is for maintaining good frequency stability of the circuit 100. Next, the operation of the temperature-sensitive voltage generator 100 will be explained.

Let the base-emitter voltages of transistors T, l, T, and 2 be BE1 and VBE2, and let the collector current be IC, respectively.
1, IC2, the following relational expression holds true if the base voltage and collector voltage are at approximately the same potential. However, IS
l and IS2 are the reverse saturation currents of the transistors T, , T, and 2, respectively, k is the Boltzmann constant, q is the amount of electron charge, and T is the absolute temperature.

The differential amplifier A1 includes a resistor 14 and transistors T, 2 and T,
Since negative feedback is applied to the differential amplifier A2 through the resistor 15 and the transistor T2, the inverting inputs of the differential amplifiers Al and A2 are both at ground potential. . Furthermore, since the input impedances of the differential amplifiers A and A2 are sufficiently high, ICl and IC2 become as follows.

However, Cc is the power supply voltage. The output voltage of the differential amplifier A1 is VT, and the base voltage of the transistor T,2 is B1.
Then, holds true.

Since the bases of the transistors T, l are grounded and the emitters of the transistors T, l, T, 2 are connected, the following equation holds true. If we take the ratio of equations (2) and (1), we get:

Here, since the characteristics of the transistors T, .

By substituting equation (6) into equation (7), the following equation is obtained.

If we take the ratio of equations (4) and (3), we get:

Equations (5), (8), and (9) hold true.

Therefore, VT becomes as follows. However, KT=-10(1
+ Shigu) 1n I soup. KT becomes a constant independent of temperature T, and T becomes proportional to temperature T.

Therefore, the voltage VT is generated at the terminal 10 as a temperature-sensitive voltage that changes in proportion to the temperature. From equation (2), temperature-sensing voltage V
It can be seen that T is determined only by the two resistance ratios R4/R3 and Rl/R2 and is independent of the power supply voltage Vcc. This shows that the temperature-sensitive voltage generator 100 has an excellent feature of not being affected by power supply voltage fluctuations, and the temperature-sensitive voltage VT is equal to the input voltage of the subsequent input signal conversion circuit 2. When you think about how familiar they are, this is a big advantage. FIG. 1 shows an analog multiplier 22 as a block diagram as a specific embodiment of the input signal conversion circuit 2. As shown in FIG.

This analog multiplier 22 may be of any type as long as it outputs a voltage proportional to the product of two input voltages, such as a well-known analog multiplier or a well-known voltage-controlled amplifier whose gain is linearly varied by a control voltage. may also be used. As described above, since the analog multiplier 22 has a high input voltage VIN applied to the terminal 20 and the input impedance of the temperature sensitive voltage VT amplifier A3, the IR is as follows.

However, CO is the power supply voltage. Since the bases of the transistors T, 3 are grounded and the emitters of the transistors T, 3, T, 4 are connected, if the base potential of the transistors T, 4 is set to B2, the following equation holds true. 03, (self)
If we take the ratio of the expressions, we get .

Here, since the characteristics of the transistors T, .

By substituting equations 04) and (15) into equation (17), the following equation is obtained. ) On the other hand, VB2 is the output voltage VTC of the input signal conversion circuit 2 divided by the resistors 32 and 33.

Now, by substituting the formula (self) representing the input voltage VTC into the formula of the company, we get: By eliminating the temperature T in the numerator and denominator, the output current 1c of the antilogarithmic amplifier 3 is as follows. It is shown by the formula.

As shown in equation (21), the output current I of the antilogarithmic amplifier 3
Since c does not include temperature T, it can be seen that it is safe against temperature changes.

Next, FIG. 2 shows an embodiment in which the present inverse logarithmic conversion circuit is applied to a sound source device for an electronic musical instrument, particularly a music synthesizer.

The music synthesizer uses a VCO (voltage controlled oscillator) or CCO (current controlled oscillator) as a sound source, and obtains a step frequency corresponding to the pressed key.

In other words, the VCO (or CCO) is controlled by the geometric voltage (or geometric current) obtained by anti-logarithmically converting the arithmetic voltage corresponding to each key using an anti-logarithmic amplifier to obtain the scale frequency corresponding to the pitch of each key. Many methods are used. Moreover, most antilogarithmic amplifiers use PN junctions such as transistors and diodes as antilogarithmic conversion elements, and as mentioned at the beginning, temperature compensation of antilogarithmic conversion characteristics has traditionally been incomplete. As a result, the temperature stability of the sound source frequency of the Miyujitsuk synthesizer was extremely poor.
In FIG. 2, the present inverse logarithmic conversion circuit is used to realize a music synthesizer sound source device with good temperature stability of the sound source frequency.

In the embodiment shown in FIG. 2, the key voltage generation circuit 2-1 and the pitch
Two input signal conversion circuits are used: a shift voltage generation circuit 2-2.

Further, the temperature-sensitive electric signal generator 1 outputs the temperature-sensitive voltage VT and at the same time outputs the temperature-sensitive current T that changes in proportion to the absolute temperature. The embodiment shown in FIG. 2 will be described in detail.

Reference numeral 1 denotes a temperature-sensitive electrical signal generator, which outputs a temperature-sensitive voltage VT and a temperature-sensitive current 8, which change in proportion to the absolute temperature T, to terminals 10, respectively.
, 10-1.

In the temperature-sensitive electric signal generator 1, 10 as indicated by the block
0 is a circuit completely similar to the temperature-sensitive voltage generator 100 in FIG.
Output. A4 is a differential amplifier, and together with resistors 105 and 106, which are stable against temperature changes, constitutes a well-known inverting amplifier. 102 to 104 are resistors that are stable against temperature changes, A is a high input impedance differential amplifier,
101 is a FET (field effect transistor).

FETlOl, differential amplifier A, and resistors 102 to 104 constitute a well-known current source, and differential amplifier A
Since the inverting input and non-inverting input of 5 are kept at the same potential,
The output signal 1T appearing at the drain of FETlOl is the voltage across the resistor 103 divided by the resistance value R6 of the resistor 102.

The voltage across the resistor 103 is as follows: If the gain of the inverting amplifier made up of the differential amplifier A4 is -G (G is a positive constant), a voltage of -GVT is generated at the output of the inverting amplifier. becomes.

Therefore, the output signal 1T is expressed by the following equation. However, K
Since O=07(1+G) and RO(R.,+RO), VT=KTT, the equation (22) becomes.

Since both KT and Kc are constants unrelated to temperature T, current 1T is proportional to temperature T. Reference numeral 2-1 denotes a key voltage generation circuit which is one of the embodiments of the input signal conversion circuit, and generates an arithmetic voltage that changes in proportion to absolute temperature and corresponds to the pressed key.

It can be said that the "input signal" to the key voltage generation circuit 2-1 is key press selection information. A6 is a differential amplifier with high input impedance, and constitutes a voltage follower that outputs the voltage of bus bar 12-11 with low impedance.

2-12 to 2-15 have mutually equal resistance values R, are stable resistors against temperature changes, and are connected in series.

One end of the resistor 2-12 is grounded, and one end of the resistor 2-15 is connected to the output terminal 10-1 of the temperature-sensitive electric signal generator 1. The key switches are drawn in such a way that the higher the key switch is located in Figure 2, the higher the scale frequency it corresponds to. Therefore, the oth key ・
The switch (key switch whose terminal is grounded) corresponds to the lowest scale frequency. Now all the keys
・When the switch is in the OFF state, an equal voltage RIT is generated between the terminals of two adjacent keys and the switch.

Any one key - When the switch is turned on, the key that was turned on - The switch end terminal voltage is equal to the bus bar 2 -
11, is converted to low impedance by a voltage follower, and is output. When multiple keys/switches are turned on at the same time, all the turned-on keys/switches are short-circuited by bus bar 12-11 and have the same potential, so the key/switch that is turned on corresponds to the lowest scale frequency among the turned-on keys/switches. The key switch voltage is output. That is, the key voltage generation circuit 2-1 has a function of generating an arithmetic scale voltage giving priority to bass notes. Now, as shown in Figure 2,
If the nth key switch is turned on, the output voltage of the key voltage generation circuit 2-1 is VTCI.

Substituting equation (23) into equation 12, we get N, R
, KT, KO are constants independent of temperature T, so voltage VTOI is proportional to temperature T. Also, (25
), it can be seen that the output voltage VTCI is also proportional to the key switch number n, which can be regarded as an "input signal". Next, 2-2 is a pitch shift voltage generation circuit, which is one of the embodiments of the input signal conversion circuit, and generates a voltage that changes in proportion to absolute temperature and whose setting level can be changed by manual operation. Occur.

This pitch shift voltage generation circuit 2-2 shifts the plurality of scale frequencies that can be selected by the key voltage generation circuit 2-1 as a whole to transpose it to a desired range or tune it to a desired frequency. This is a circuit for In addition, the "input signal" to the pitch shift voltage generation circuit 2-2
can be said to be the setting position information of the variable resistor. 2-20
is a three-terminal variable resistor, the first terminal 2-21 is grounded, and the third terminal 2-23 is applied with a temperature-sensitive voltage VT.

Output voltage VTO of the pitch shift voltage generation circuit 2-2
2 is taken out from the 2nd terminal 2-22 of the 3-terminal variable resistor 2-20. No. 2 terminal 2-22 is 3-terminal variable resistor 2
If it is located at α times the total resistance value of -20 (0≦α≦1), the voltage appearing at the second terminal 2-22, that is, VTO2, is expressed by the following equation.

From the Q1 formula, VT=KTT, so the formula (26) is
Therefore, the output voltage VTC2 is proportional to the temperature.

Also, through 12 trials, the output voltage VTC2 is the "input signal"
It can be seen that it is also proportional to a constant α representing the setting position of the three-terminal variable resistor 2-220, which can be regarded as . 3 is a two-input anti-logarithmic amplifier, which is a circuit in which the resistor 33 in the anti-logarithmic amplifier 3 shown in FIG. do.

However, the Q ladder type VB2 is the transistor Tr in FIG.
It is replaced by the base potential VB3 of 4. That is, the equation representing the output current C of the antilogarithmic amplifier 3 in FIG. 2 is as follows. Note that both the resistors 36 and 37 are stable against temperature changes.

Now, from FIG. 2, the base potential V of the transistor Tr4
B3 is expressed by the following formula.

However, K1= 11D11A RAR0+RORD+RDRA be.

Substituting the (29) into equation (28), we get: Voltage TC
By substituting equations (25) and (27) representing l, TC2 into equation (30), we get the following equation, and by eliminating the temperature T in the numerator and denominator, the output current 1c of the antilogarithmic amplifier 3 becomes It is shown by the formula.

As shown in equation (31), the output current c of the inverse logarithmic amplifier 3 in FIG. 2 does not include the temperature T, so it can be seen that it is stable against temperature changes.

Reference numeral 4 in FIG. 2 is a current controlled oscillator, which oscillates at a frequency f that is directly proportional to the control current 10. This frequency f becomes the sound source frequency. That is, when the proportionality constant is KO, the sound source frequency f is expressed by the following equation. By substituting equation (31) into equation (32), the sound source frequency f is expressed as follows.

If the temperature stability of the current controlled oscillator 4 is good, the proportionality constant K
. is stable against temperature changes, temperature T is not included in equation (33), and sound source frequency f is stable against temperature changes. In particular, the temperature T in the exponential term is eliminated, and the temperature stability for the geometrical change in the sound source frequency f is extremely high. Equation (33) shows that the sound source frequency f is the keyboard information (indicating which key is being pressed) n
and pitch shift information (indicating how much the sound source frequency has been shifted) α.

Both n and α are in the exponential term, and an arithmetic change in n or α appears as a geometric change in the sound source frequency f. By setting each constant in equation (33) so that the sound source device has the desired characteristics, a sound source device whose sound source frequency f is completely unaffected by temperature changes can be obtained.

In actual circuit fabrication, as shown in FIG. For example, by placing them close together, mold-packing them together, or at the same temperature equilibrium.
It is necessary to take into account the use of the four transistors on the C chip when designing. Above, in Fig. 2, we have described an example of the anti-logarithmic conversion circuit applied to the sound source device of the Miyuszczyk synthesizer.As seen in the figure,
There may be not only one input signal conversion circuit but a plurality of input signal conversion circuits for one antilogarithmic amplifier.

Further, the number of anti-logarithmic amplifiers is not limited to just one, but may be multiple. However, in this case, the PN of the semiconductor in each antilogarithm amplifier is
Of course, it is necessary to keep the junction and the PN junction of the semiconductor in the temperature-sensitive electrical signal generator under substantially the same temperature. In addition, in FIG. 2, an embodiment of the music synthesizer sound source device to which the present invention is applied is described using 4 as a current controlled oscillator, but 4 has a cut-off frequency (or resonant frequency) proportional to the control current Ic. Using a variable current control filter, change the name of 2-2 to cut-off frequency shift voltage generation circuit (or resonance frequency shift voltage generation circuit), and use the signal obtained by passing the sound source signal through the current control filter as a musical tone signal. With this configuration, like the above-mentioned sound source device, the system shown in FIG. 2 becomes a tone color control device for a music synthesizer to which the present invention is applied.

That is, the present invention is very effective when applied to a timbre control device for a music synthesizer. Finally, the first
FIG. 3 shows an embodiment of the input signal conversion circuit 2 when the input signal input to the input signal conversion circuit 2 shown in the figure is a digital signal.

In FIG. 3, 2 is R-2 as an input signal conversion circuit.
This is a 4-bit D/A converter using an R-ladder type resistor network.

A7 is a differential amplifier, which together with the feedback resistor Rf constitutes a current-to-voltage converter. S1 to S4 are current switches, which are switched and controlled by digital input signals Q1 to Q4 applied to input terminals 20-1 to 20-4, respectively. Since the temperature-sensitive voltage T is applied to the terminal 10 as the reference lens voltage of the D/A converter 2, the current flowing through the current switches S1 to S4 is 8.-16r, respectively.
VTVTVT4 ・? ,2・−,? becomes.

Current switch 1rr16r16r switch SO (n=1 to 4) is digital input signal Qn(
When Qn (n=1 to 4) is "1", it is connected to the inverting input side of the differential amplifier A, and when Qn is "0", it is connected to the ground side.

Therefore, if QO represents the numbers 1 and 0 as opposed to logic "1" and "O", then the output voltage VTC appearing at the output terminal 21 will be.

From equation (substitution), since VT2KTT, equation (34) becomes as follows.

From equation (35), if Rf/r is stable against temperature changes, the output voltage VTO will change in proportion to the temperature T. In the embodiment shown in FIG. 3, a 4-bit digital signal is used for convenience of explanation, but it is clear that the embodiment can be realized without any restriction on the number of bits. As described above, the present invention eliminates at once the difficulty of temperature compensation for the antilogarithmic conversion characteristics that antilogarithmic converters that use semiconductor PN junctions as antilogarithmic conversion elements have, and also requires no adjustment. This makes it possible to completely compensate for the temperature without any variation, and is of great value as it can significantly improve the temperature stability of devices to which anti-logarithmic converters are applied, such as music synthesizers.

[Brief explanation of the drawing]

FIG. 1 is a specific circuit configuration diagram of an embodiment of the present invention, FIG. 2 is a specific circuit configuration diagram of an embodiment in which the present invention is applied to a music synthesizer sound source device, and FIG. 3 is similar to FIG. 1. FIG. 3 is a specific circuit configuration diagram of another embodiment of the input signal conversion circuit 2 shown in FIG. DESCRIPTION OF SYMBOLS 1... Temperature-sensitive electric signal generator, 2... Input signal conversion circuit, 3... Anti-logarithmic amplifier, 100
... Temperature-sensitive voltage generator, 22 ... Analog multiplier, 2-1 ... Key voltage generation circuit, 2-2
...Pitch shift voltage generation circuit.

Claims (1)

[Claims] 1. A temperature-sensitive electrical signal generator that includes a PN junction of a first semiconductor as a temperature-sensitive element and generates an electrical signal that changes in proportion to absolute temperature, an input signal, and the temperature-sensitive electrical signal. at least one input signal conversion circuit that receives the output electric signal of the generator and generates an electric signal that changes in proportion to the absolute temperature and is proportional to the input signal; and a second input signal conversion circuit as an anti-log conversion element. an antilogarithmic amplifier that includes a semiconductor PN junction and performs an antilogarithmic conversion of the output electrical signal of the input signal conversion circuit, the first and second semiconductor PN junctions are brought to substantially the same temperature; An anti-logarithmic conversion circuit characterized in that the anti-logarithmic amplifier is temperature-compensated by an output electrical signal from a temperature-sensitive electrical signal generator. 2. The inverse logarithmic conversion circuit according to claim 1, wherein the temperature-sensitive electric signal generator generates a voltage that changes in proportion to absolute temperature. 3. The anti-logarithmic conversion circuit according to claim 2, which uses a first pair of transistors having mutually matched voltage-current characteristics as a PN junction of the first semiconductor. 4. The temperature-sensitive electric signal generator further includes first and second differential amplifiers, and first, second, third, fourth, and fifth resistors, and the first and second differential amplifiers The inverting inputs of the amplifiers are connected to a constant voltage source via the first and second resistors, respectively, the non-inverting inputs of the first and second differential amplifiers are substantially grounded, and the third One end of the resistor and the base of one transistor of the first set of paired transistors are respectively grounded, and the collector of the upper first transistor and the collector of the other transistor of the first set of paired transistors are respectively grounded. connected to inverting inputs of first and second differential amplifiers, and connecting the output of the second differential amplifier to the emitter of the other transistor via the fifth resistor;
The emitter of the one transistor is connected to the emitter of the other transistor, the base of the other transistor is connected to the other end of the third resistor, and the output of the first differential amplifier is connected to the emitter of the other transistor. 4. The anti-logarithmic conversion circuit according to claim 3, wherein the anti-logarithm conversion circuit is connected to the base of the other transistor via a resistor so as to output the output voltage of the first differential amplifier. 5 Claim 1 in which the temperature-sensitive electric signal generator generates voltage and current that change in proportion to absolute temperature
The anti-logarithm conversion circuit described in Section 1. 6. The anti-logarithmic conversion circuit according to claim 1, wherein the PN junctions of the first and second semiconductors are in the same package. 7. A first pair of transistors with uniform voltage-current characteristics are used as the PN junction of the first semiconductor, and a second pair of transistors with uniform voltage-current characteristics are used as the PN junction of the second semiconductor. An anti-logarithm conversion circuit according to claim 1, which uses transistors. 8. The anti-logarithm conversion circuit according to claim 7, wherein the first and second pairs of transistors are in the same package. 9 The antilogarithmic amplifier further includes a differential amplifier, a first, a second,
third and fourth resistors, substantially grounding the non-inverting input of the differential amplifier, and connecting the base of one transistor of the second pair of transistors to the second resistor. one end of the differential amplifier is grounded, the inverting input of the differential amplifier is connected to a constant voltage source via the first resistor, the collector of one of the transistors is connected to the inverting input of the differential amplifier, and the connecting the output of the differential amplifier to the emitter of the one transistor through the fourth resistor, and connecting the emitter of the other transistor of the second pair of transistors to the emitter of the one transistor; The other end of the second resistor is connected to the base of the other transistor, one end of the third resistor is connected to the base of the other transistor, and the other end of the third resistor is connected to the base of the other transistor. 8. The anti-logarithmic conversion circuit according to claim 7, wherein the inverse logarithmic conversion circuit is configured to have a voltage input terminal and a collector of the other transistor as a current output terminal. 10. The inverse logarithmic conversion circuit according to claim 1, wherein the input signal to the input signal conversion circuit is given as electrical signal switching selection information by a switch. 11. The anti-logarithmic conversion circuit according to claim 10, which uses an electronic switch as the switch. 12. The anti-logarithmic conversion circuit according to claim 10, which uses a mechanical switch as the switch. 13. The inverse logarithmic conversion circuit according to claim 12, which uses a key switch having a busbar as the mechanical switch. 14 As an input signal conversion circuit, both terminals of adjacent key switches of a plurality of key switches having a common bus bar are connected through resistors, and the key switch corresponding to the lowest tone (or highest temperature) is connected. It has a keyboard for an electronic musical instrument whose terminal is connected to a fixed potential point, and a voltage follower, and the output current of the temperature-sensitive electric signal generator is connected to the highest note (or lowest note) of the keyboard. The key corresponding to
14. The inverse logarithm conversion circuit according to claim 13, which uses an input signal conversion circuit configured to lead to a terminal of a switch, convert the busbar voltage when the key is turned on to impedance with the voltage follower, and output the resultant signal. 15. The anti-logarithmic conversion circuit according to claim 1, wherein the input signal to the input signal conversion circuit is given as setting position information of a substantial movable contact of a variable resistance resistor. 16 A variable resistance resistor is provided in the preceding stage of the input signal conversion circuit, and an input signal is provided to the variable resistance resistor, and a substantial variable electrode of the variable resistance resistance provides an input signal to the input signal conversion circuit. An inverse logarithmic conversion circuit according to claim 15, wherein the inverse logarithm conversion circuit is configured as follows. 17. The anti-logarithmic conversion circuit according to claim 1, wherein the input signal to the input signal conversion circuit is provided as an analog signal. 18. The anti-logarithmic conversion circuit according to claim 17, wherein the input signal conversion circuit is an analog multiplication circuit that multiplies the output electric signal of the temperature-sensitive electric signal generator by the input signal. 19. The anti-logarithmic conversion circuit according to claim 18, which uses an analog multiplier as the analog multiplication circuit. 20. The anti-logarithmic conversion circuit according to claim 1, wherein the input signal of the input signal conversion circuit is provided as a digital signal. 21 As the input signal conversion circuit, a circuit for multiplying an analog signal and a digital signal is used, and the output electric signal of the temperature-sensitive electric signal generator is multiplied by the input signal. anti-logarithm conversion circuit. 22 A D/A converter is used as a circuit for multiplying an analog signal and a digital signal, the input signal is applied to the digital input terminal, and the reference voltage application terminal of the D/A converter is connected to the temperature-sensitive electric signal generator. 22. The inverse logarithmic conversion circuit according to claim 21, wherein the inverse logarithmic conversion circuit is adapted to provide an output electrical signal.