JPH0722250B2 - Non-linear amplifier circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear amplifier circuit that obtains an output voltage that changes non-linearly with respect to an input voltage, and in particular, a non-linear voltage signal that changes non-linearly such as a resistance sensor. The present invention relates to a linear amplifier circuit that converts the output voltage of the linear amplifier.

2. Description of the Related Art FIG. 3 shows a circuit configuration of a conventional nonlinear amplifier circuit. Third
In the figure, 31 is an input terminal, 32 is an operational amplifier, 33 to 39 are resistors, 40 to 42 are diodes, 43 is an output terminal, and 44 is a bias terminal.

Then, when the input voltage is input from the input terminal 31, the operational amplifier 32 performs normal amplification, and as the input voltage increases,
The output voltage increases and the diodes 40 ... 41 are sequentially turned on. Then, the feedback resistance Rx that negatively feeds back from the output terminal 43 to the inverting input terminal of the operational amplifier 32 is sequentially switched by the conduction of the diodes 40. Here, assuming that the resistance values of the resistors _{33 to 39} are R _{33 to} R ₃₉ , the feedback resistor Rx = R ₃₅ in the first stage in which the input voltage is small and all the diodes 40 ... 41 are in the off state. However, the second stage when the input voltage becomes a little higher and the diode 40 conducts is the feedback resistance Rx = R ₃₅ R
₃₆ / (R ₃₅ + R ₃₆ ) Moreover the input voltage is increased, the third stage of the diode 40 ... 41 conducts the feedback resistor _{Rx = R 35 R 36 R 37} / (R 35 R 36 + R 36 R 37 + R 37 R 35) and so as In addition, the feedback resistance Rx changes so that the parallel circuit of the resistance increases as the input voltage increases, and the resistance value gradually decreases.

On the other hand, in this circuit, since the voltage amplification degree is determined by (1 + Rx / R ₃₄ ), the voltage amplification degree changes according to the level of the input voltage, and as a result, the function is converted into a pseudo function.

Problems to be Solved by the Invention In the conventional configuration as described above, it is possible to compensate the temperature characteristic of the resistance value, but it is not possible to compensate the temperature characteristic of the forward diode voltage of the diode, It is a problem that the level of the output voltage conducted by each diode varies depending on the temperature.

The present invention solves such a problem, and an object of the present invention is to provide a non-linear amplification circuit that operates safely against temperature changes.

Means for Solving the Problems The nonlinear amplification circuit of the present invention comprises a differential pair of one conductivity type transistors, and a one conductivity type transistor in which a base is connected to an output of the differential pair and a first resistor is connected to a collector. A first differential amplifier having an output transistor and an emitter output of the output transistor feedback-coupled to an inverting input terminal of the differential pair; and an output of the differential pair of the reverse conductivity type transistor as an emitter follower. A plurality of structures of a second differential amplifier, which is configured to output and whose emitter follower output is feedback-coupled to an inverting input terminal of a differential pair of the reverse conductivity type transistor, and the emitter follower outputs of the plurality of structures and the output. Individual low antibodies are connected between the emitter outputs of the transistor for application, different reference potentials are input to the respective non-inverting input terminals of the plurality of structures, and the non-inverting input terminal of the first differential amplifier is connected. The input voltage is applied to and the output voltage is taken out from between the terminals of the first resistor.

Operation With this configuration, the first differential amplifier functions as an input voltage follower, the emitter output of the output transistor outputs a voltage equal to the input voltage with low impedance, and each of the second differential amplifiers The emitter follower outputs also operate with low impedance, and output voltages equal to the different reference potentials that are input. When the emitter output potential of the first differential amplifier becomes higher than the emitter follower output potential, a current corresponding to the voltage difference between the reference potential and the input voltage flows through the resistor connected to the emitter follower output. This current is added to the operating current of the output transistor of the first differential amplifier, and the output voltage that changes non-linearly with respect to the input voltage is output from between the terminals of the first resistor.

Embodiment An embodiment relating to the nonlinear amplifier circuit of the present invention will be described below with reference to FIG. 1 showing a circuit configuration diagram thereof.

In FIG. 1, reference numeral 11 is a first differential amplifier mainly composed of a differential pair of NPN type transistors, and 12, 13, 14 are second differential amplifiers mainly composed of a differential pair of PNP type transistors. . Further, 15 is an input terminal to which an input voltage is input, Vcc is a power supply voltage terminal to which a power supply voltage is supplied, 16 is a reference voltage terminal to which a reference voltage is supplied, 17 to 23,111,1201 to 1204 and 1301.
~ 1304 is a resistance, 112 ~ 114, 1205 ~ 1207 and 1305 ~ 1307
Is an NPN transistor, 115, 116, 1208 to 1211 and 1308
1311 are PNP transistors, 117, 1212 and 1312 are constant current sources, and 24 to 27 are contacts.

Here, the first differential amplifier 11 couples a differential pair of NPN transistors 112 and 113 whose emitters are commonly connected, a constant current source 117 which supplies a current to the common node of the emitters, and a collector of the transistors 112 and 113. PNP type transistor 11
5, 116, and an output terminal of the differential pair (collector of the transistor 113) and an output NPN transistor 114 that outputs a voltage. The emitter output 27 of the transistor 114 is the base of the transistor 113 (differential of the transistor 1211). It is for outputting with low impedance from the emitter output, and for outputting the voltage V ₂₅ of the latter differential amplifier 13 and contact 25 with low impedance from the emitter output of the transistor 1311. 14 is the voltage of contact 16
It is for outputting V ₂₆ with low impedance.

Next, the circuit operation of the embodiment shown in FIG. 1 will be described in detail. First, when a voltage V ₂₇ and V ₂₄ of the contacts 27 and 24 of the V ₂₇ <V _24, the transistor 1209 is turned on, the transistor 1210 is turned off, the transistor 1207,1206 and transistors are connected to the collector of the transistor 1210 1211,12
05,1208 is turned off, so the current I ₁₂₀₃
Does not flow and is negligible transistor 1209
The differential amplifier 12 is basically in the off state only when the base current of the current flows to the resistor 17.

On the contrary, when the voltages V ₂₇ and V ₂₄ of the contacts 27 and 24 become V ₂₇ > V ₂₄ , the transistor 1209 is turned off and the transistor 1210 is turned off.
Is turned on, and transistors 1207 and 1206 and transistors 1211 and 1211 connected to the collector of the transistor 1210 are turned on.
The 1205 and 1208 are turned on, and the current I ₁₂₀₃ flows through the resistor 1203. As a result, the differential amplifier 12 is basically turned on, a voltage equal to the reference voltage V ₂₄ is output to the emitter output of the transistor 1211 with low impedance, and the resistor 17 is connected from the contact 27 to the output terminal of the differential amplifier 12. A current I ₁₇ flows toward (the emitter of the transistor 1211). This current can be expressed by I ₁₇ = (V ₂₇ −V ₂₄ ) / R ₁₇ (1) assuming that the resistance value of the resistor 17 is R ₁₇ . The differential amplifier 13 of the same type as the above differential amplifier 12 operates in the same manner, and the contact 27
If the voltages V ₂₇ and V ₂₅ of V and ₂₅ are V ₂₇ <V ₂₅ , the differential amplifier 13 is basically in the OFF state, and if V ₂₇ > V ₂₅ , the resistor 18 is connected to the differential amplifier 13 via the contact 27. A current I ₁₈ flows toward the output terminal (the emitter of the transistor 1311). This current can be expressed by the following equation, assuming that the resistance value of the resistor 18 is R ₁₈ .

I ₁₈ = (V ₂₇ −V ₂₅ ) / R ₁₈ (2) Further, the differential amplifier 14 of the same type as the above differential amplifier 12 operates in the same manner, and the voltage V ₂₇ of the contacts 27 and 26 becomes V ₂₆ is V
_{When 27} <V ₂₆ , the differential amplifier 14 is basically turned off, and when V ₂₇ > V ₂₆ , the differential amplifier 14 is connected from the contact 27 to the resistor 19.
A current I ₁₉ flows toward the output terminal of 14. This current can be expressed by the following equation, assuming that the resistance value of the resistor 19 is R ₁₉ .

I ₁₉ = (V ₂₇ −V ₂₆ ) / R ₁₉ (3) Therefore, when the input voltage input from the input terminal 15 gradually increases from the ground potential, the differential amplifier 14 with a low reference potential is used.
The second differential amplifiers are sequentially activated in the order from 13 to 12, and are connected between the second differential amplifiers 12 to 14 and the output terminal 27 of the first differential amplifier 11. The current flowing through the resistors 17 to 19 is added to the output current of the first differential amplifier 11. From this, the output current I ₂₇ of the first differential amplifier 11 changes according to the voltage level of the contact 27 as follows.

When V ₂₅ ＞ V ₂₇ ＞ V ₂₆ I ₂₇ ＝ I ₁₉ …… (4) When V ₂₄ ＞ V ₂₇ ＞ V ₂₅ I ₂₇ ＝ I ₁₉ ＋ I ₁₈ …… (5) When V ₂₇ ＞ V ₂₄ I ₂₇ = I ₁₉ + I ₁₈ + I ₁₇ (6) The output current of the first differential amplifier 11 is the emitter current of the transistor 114, which is almost equal to the collector current of the transistor 114, and the current I ₁₁₁ flowing through the resistor ₁₁₁ is You can think of I ₁₁₁ = I ₂₇ . When the output voltage of this circuit is taken out from between the terminals of this resistance (first resistance) 111, an output voltage V ₁₁₁ that changes non-linearly with respect to the input voltage as shown in FIG. 2 is obtained. _Inflection points V _OUT1 and V _OUT2 of the output voltage V _{111 in} FIG.
Is given by

V _OUT1 = (V ₂₅ −V ₂₆ ) R ₁₁₁ / R ₁₉ V _OUT2 = (V ₂₄ −V ₂₆ ) R ₁₁₁ / R ₁₉ + (V ₂₄ −V ₂₅ ) R ₁₁₁ / R ₁₈ Here, consider the temperature characteristics. Looking at it, the reference voltage terminal
If the voltage V _{16 of 16} is stable and the resistors are made of the same material, the setting of reference potentials V _{24 to} V ₂₆ with different potentials will be stable, and each voltage follower using a differential amplifier will provide input / output gain. Since it is kept constant, for example, the current I _{17 to} I ₁₉ flowing through the resistors 17 to ₁₉
Of the output voltage V ₁₁₁
Is temperature-compensated by the relative ratio of the resistors 17 to 19 and the resistor 111, and operates stably with respect to the ambient temperature.

In this embodiment, the transistors forming the first differential amplifier 11 and the second differential amplifiers 12 to 14 can be formed by using transistors of opposite polarities, and the same effect can be obtained. It goes without saying that it will be done.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to realize a non-linear amplifier circuit that operates stably with respect to temperature changes and obtains an output voltage that changes non-linearly with respect to changes in the input voltage.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a non-linear amplifier circuit according to an embodiment of the present invention, FIG. 2 is an input / output characteristic diagram of the circuit of FIG. 1, and FIG. 3 is a circuit configuration diagram of a conventional non-linear amplifier circuit. is there. 11 ... First differential amplifier, 12-14 ... Second differential amplifier, 15 ... Input terminal, 16 ... Reference voltage terminal, 17-23, 11
1,1201 to 1204,1301 to 1304 ... Resistance, 112 to 114,1205 to 12
07,1305〜1307 …… NPN type transistor, 115,116,1208〜
1211,1308〜1311 …… PNP type transistor, 117,1212,131
2 ... Constant current source, Vcc ... Power supply voltage terminal.

Claims (1)

[Claims] 1. A differential pair of one conductivity type transistors, and a single conductivity type output transistor having a base connected to the output of the differential pair and a first resistor connected to the collector, A first differential amplifier in which the emitter output of the transistor is feedback-coupled to the inverting input terminal of the differential pair, and the output of the differential pair of the reverse conductivity type transistor is output in an emitter follower configuration, and the emitter follower output is output in the reverse direction. A plurality of structures of a second differential amplifier, which are feedback-coupled to the inverting input ends of the differential pair of conductivity type transistors, and are respectively provided between the inverting input ends of the plurality of structures and the emitter output of the output transistor. Individual low antibodies are connected, different reference potentials are input to the emitter follower outputs of the plurality of structures, an input signal is applied to the non-inverting input terminal of the first differential amplifier, and terminals of the first resistor are connected. Nonlinear amplification circuit, characterized in that taking out et output voltage.