JPS63236178A - Multiplying circuit - Google Patents

Abstract

PURPOSE:To constitute an analog multiplying circuit having high accuracy, which is not influenced by a variation of an ambient temperature, by using a simple temperature compensating circuit. CONSTITUTION:A temperature compensating circuit (b) is inserted into a bias current circuit. That is, when the temperature compensating circuit (b) is used, a bias current Ia can be shown by Ia=VL/R3. In this regard, VL and R3 denote a fixed potential of a point L, and a constant of a resistance 20, respectively. A proportional constant K is K=RLXR3/(R1XR2XVL). In this case, VL denote a (+) input terminal voltage, namely, a fixed voltage having no temperature coefficient of an operational amplifier 21, and on the other hand, the resistances RL, R1, R2 and R3 can have the same temperature coefficient, respectively, since they are formed by using the same diffused resistor, in case of forming this multiplying circuit by an IC. Accordingly, the temperature coefficient can be canceled by a numerator and a denominator, and the proportional constant K of the multiplying circuit has no temperature coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multiplication circuit with a humidity compensation circuit. Conventionally, analog multiplication circuits such as multiplayer type multipliers formed on semiconductor integrated circuits (IC) are affected by internal resistance or a large temperature coefficient of bias current on their calculation output (proportionality constant), making it difficult to obtain accurate calculation output. It was difficult.

SUMMARY OF THE INVENTION An object of the present invention is to use a temperature compensation circuit to make the temperature coefficient of the proportionality constant of the II multiplication circuit zero, thereby configuring a multiplication circuit that is not affected by the ambient temperature.

The present invention will be explained below using the drawings.

FIG. 1 is a circuit diagram of a (-) embodiment of the present invention;
The main multiplication circuit is the temperature compensation circuit.

In the figure: 1.2, 8, 9. 12, 16, 17° 20.
22.23 are the respective resistances, 3.4.5.6°7.10.1
3, 14, 15, 18, and 19, the NPN transistor 21 and the differential amplifier circuit (hereinafter referred to as an operational amplifier) 11 are current sources.

The operation of this circuit is to apply a power supply voltage between terminals A and B, apply an input voltage Vinl between terminals E and F, and apply an input voltage Vin-2 to terminals GH@. , c-o
During this time, an output voltage Vo (3111 output) is generated.

At this time, the relationship between the input voltage and the output voltage is expressed by the following equation.

VO-KxVin-1xVin-2++ (1) In this equation, K is a proportionality constant, which is expressed by the following equation.

K=RL/(R4xR2x Ia l -(2
) and R are the constants of the resistors (and resistors 2, R1 is the constant of resistors 8 and 9, R2 is the constant of resistors 16 and 17, and la is the current value (bias current) flowing through point K.

Here, this lL) main circuit I is RL, R1, R2
, la have their own temperature coefficients determined by their respective temperature coefficients.

Therefore, if the bias current 1a is set to flow in the direction of the dotted arrow in the figure, the above-mentioned temperature drift problem occurs. Therefore, the present invention is simple! The above-mentioned problem is solved by inserting a degree compensation circuit (b) into the bias current circuit. That is, using the temperature compensation circuit port, the bias N current 1a can be expressed by the following equation.

la =VL/R3-(3) where VL is a fixed potential at point L, and R3 is a constant of the resistor 20.

Substituting equation (3) into equation (2), -RLxR3/ (R1xR2xVL) - (4) Here, VL is the (+) input terminal voltage of the operational amplifier 21, that is, a fixed voltage without a temperature coefficient; Resistance RL
, R4, R2, and R3 are formed using the same diffused resistor when this Ift circuit is formed using an IC, so they can each have the same temperature coefficient. Therefore, in equation (4), these temperature coefficients can be canceled between the numerator and denominator, and the proportionality constant of the multiplication circuit does not have a temperature coefficient.

FIG. 2 is a circuit diagram of another embodiment of the present invention, and the difference from the above embodiment is that the output of the operational amplifier 28 is connected to the transistor 24.
．． The voltage is applied via a current mirror circuit consisting of 26 and 27, and the same effect can be obtained by this.

As is clear from the above description, according to the present invention, a high-precision analog multiplication circuit that is not affected by ambient temperature changes can be constructed by using a low-temperature compensation circuit, and is therefore particularly suitable for IC implementation. The practical effects are great.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams of embodiments of the present invention. In the figure, (A) is the main multiplication circuit, (B), (C)A is the '6A degree compensation circuit, 21.28 is the differential amplification circuit, and 19
．． 24 is a transistor.

Claims (1)

[Claims] A differential amplification circuit, a circuit for fixing the potential of the (+) input terminal of the differential amplification circuit, and a circuit between the (-) input terminal and the output terminal of the differential amplification circuit. A multiplication circuit comprising a transistor whose emitter and base are connected, and an emmic resistor of the transistor, the collector side of the transistor being connected to a bias current path of the multiplication circuit directly or via a current mirror circuit.