JPS6343786B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved analog multiplier.

Conventionally, this type of multiplier first logarithmically transforms two inputs A and B, performs addition, and transforms the result into an inverse logarithm to obtain C=A.B. Therefore, this method not only requires four functions: two logarithmic converters, an adder, and an antilogarithmic converter, but also a compensation circuit for the drift of these converters due to temperature changes. It is necessary to provide
The drawback was that the circuit configuration became increasingly complex.

In order to eliminate the drawbacks of the above-mentioned conventional example, the present invention provides a voltage/impedance converter formed on one pellet and composed of two transistors with uniform characteristics and an operational amplifier, and this voltage/impedance converter. A simple configuration that has an input means for regulating the current flowing through the output impedance of the input means, and outputs a multiplied voltage obtained by multiplying the voltage input to the input means by the voltage input to the voltage/impedance converter. This provides a highly accurate analog multiplier with easy temperature compensation. Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows one embodiment of the present invention.
OP ₁ and OP ₂ are operational amplifiers with high input impedance in both DC and AC, and there is no input offset voltage. Q ₁ and Q ₂ are formed close to each other on the same pellet, have almost the same properties,
In particular, it is a field effect transistor with matched mutual conductance (gm). Both field effect transistors Q ₁ and Q ₂ have their sources grounded (Q ₂ is virtual ground), and their gates are connected to each other and to the output of the operational amplifier OP ₁ via a resistor _RG . The drain of the field effect transistor Q ₁ is connected to the constant current source S and also to the non-inverting input of the operational amplifier OP ₁ , and the drain of the field effect transistor Q 1 is connected to the non-inverting input of the operational amplifier OP ₁ , the field effect transistor Q ₁ , and the resistor.
R _G constitutes a negative feedback amplifier.

In the circuit within the dashed-dotted line frame 1 configured as described above, when input voltage E _iA is applied to the inverting input of operational amplifier OP ₁ , the output voltage of operational amplifier OP ₁ is applied to the gate of field effect transistor Q ₁ . If the internal impedance between the drain and source of _the field effect transistor _Q1 at this time is _Z1 , then the following relational expression holds true.

Z ₁ = E _iA /I _c (1) However, the operating range of E _iA is 0E _iA (+) V, and I _c is the current flowing out from the constant current source S. On the other hand, the field effect transistor Q ₁ is placed on the same pellet as Since the same gate voltage as that of one field effect transistor Q ₁ is also applied to the other field effect transistor Q ₂ which has been formed and has almost the same characteristics, especially the same mutual conductance (gm), the drain The internal impedance Z ₂ between the sources is also equal to Z ₁ , and since both transistors Q ₁ and Q ₂ are formed on the same pellet, they are equally affected by external temperature, and the The heat is immediately transferred to the other transistor, causing a similar temperature rise, and the transconductance (gm) also changes in the same way, resulting in Z ₁ = Z ₂ E _iA /I _c (2). . That is, the circuit within the dashed-dotted line frame 1 in FIG. 1 is a voltage/impedance converter that extracts an output impedance proportional to the input voltage.

Operational amplifier OP ₂ is a field effect transistor Q ₂
The internal impedance Z ₂ and the resistor R _i constitute a general inverting amplifier. And the input voltage E _iB
The following well-known equation holds true between Eput and the output voltage _Eput .

E _put = −Z ₂ /R _i E _iB (3) Therefore, from equations (2) and (3), E _put = −1/R _i I _c E _iA・E _iB = k ₁・E _iA・E _iB (4) However, k ₁ =-1/R _{i Ic} The operating range of the input voltages E _iA and E _iB is 0E _iA (+)V 0E _iB (-)V. That is, the input voltage E _iA of the voltage impedance converter and the input voltage E _iB of the inverting amplifier
The multiplied voltage obtained by multiplying by the inverting amplifier can be obtained as the output voltage of the inverting amplifier.

FIG. 2 shows another embodiment of the present invention, in which the circuit within the dashed-dotted line frame 2 is a voltage converter having the same function as the circuit within the dashed-dotted line frame 1 shown in FIG.
This is an impedance converter, and the output impedance proportional to the input voltage E _iA of this voltage/impedance converter is extracted as the internal impedance of transistor Q ₂ and used as the output load impedance for the constant current source. That is, operational amplifier OP ₂ , transistor Q ₃ and resistor R ₁ constitute a constant current circuit for resistor R ₂ ,
This constant current circuit and resistor R ₂ , resistor R ₃ , operational amplifier OP ₃ and transistor Q ₄ are transistors.
It constitutes a constant current circuit for output load impedance Z ₂ which is the internal impedance of Q ₂ .
Then, the following equation holds between the input voltage E _iB and the output voltage E _put of the operational amplifier OP ₂ .

E _put = R ₂・Z ₂ /R ₁・R ₃・E _iB (5) Therefore, by substituting equation (2) into equation (5), E _put = R ₂ /R ₁・R ₃・I _c・E _iA・E _iB =k ₂・E _iA・E _iB (6) However, k ₂ =R ₂ ／R ₁・R ₃・I _cThe operating range of input voltage E _iA・E _iB is 0E _iA (+) V 0E _iB (+)V can be obtained.

Note that if the input voltages have different polarities and you want to make them the same, you can insert an inverting amplifier into one of the inputs. Furthermore, when using the entire plus and minus ranges, it is only necessary to insert absolute circuits into both inputs. Moreover, although the case of DC signals has been described above, AC signals can also be handled in a similar configuration by applying appropriate bias voltages to each input.

As explained above, according to the present invention, two transistors with the same characteristics can be formed on the same pellet, and since the two transistors can always be kept under the same temperature condition, the characteristics of both transistors can be improved. The voltage and voltage generated by these two transistors and the operational amplifier can always be kept equal.
It is possible to extract an impedance proportional to the input voltage of the impedance converter and output a multiplied voltage obtained by multiplying the voltage input to the input means for regulating the current flowing through this impedance by the voltage input to the voltage/impedance converter. I can,
This has the advantage of providing an analog multiplier with a simple configuration and a wide operating range.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of the invention, and FIG. 2 is a circuit diagram of another embodiment of the invention. _Q1 , _Q2 ...transistor or field effect transistor, _OP1 , _OP2 ...operational amplifier, S...constant current source.

Claims (1)

[Claims] 1 Formed on one pellet with uniform properties 2
an operational amplifier whose output is applied to the bases or gates of the two transistors; the collector or drain of one of the two transistors and the non-inverting input of the operational amplifier; A voltage/impedance converter consisting of a connected constant current source, an input means for regulating the current flowing to the output impedance of the voltage/impedance converter, and a voltage input to the input means and the voltage/impedance converter. An analog multiplier comprising an output means configured to output a multiplied voltage obtained by multiplying a voltage input to the multiplier.