JPS61156910A - Differential amplifier circuit - Google Patents

Abstract

PURPOSE:To improve the temperature characteristic of an output signal by providing a differential transistor (TR) whose drain or a collector is connected to a power supply via a load and whose sources or emitters are connected in common and providing a constant current source circuit connected to the sources or the emitters connected in common. CONSTITUTION:A couple of N-channel MOSTRs Q1, Q2 whose sources are connected in common, a differential circuit A1 having load resistors R1, R2, and a constant current source circuit CS1 having a positive temperature coefficient comprising N-channel MOSTRs Q3, Q4, P-channel MOSTRs Q5, Q6 and resistors R3, R4 are provided. When temperature rises in the P-channel MOSTRs Q5, Q6, a drain current ID is increased to the same gate voltage VG and the threshold voltage of the gate is decreased. Further, a current IS1 flowing the TRQ3 increases as the temperature rises and the constant current source circuit CS1 acts on decreasing the output voltages VG1, VG2 of the differential circuit as the temperature rises. Thus, the temperature compensation of each parameter for an integrated circuit is attained completely.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a differential amplifier circuit, and in particular to a constant current source circuit that utilizes the threshold characteristics of transistors to have a predetermined temperature characteristic. This invention relates to a differential amplifier circuit with improved temperature characteristics using a current source circuit.

(Prior Art) FIG. 4 shows a conventional differential amplifier circuit. The circuit shown in the figure includes a pair of transistors Q1 and Q2 with seven sources connected to each other, a transistor Q3 for a constant current source circuit, and load resistors R1 and R2. The drain of transistor Q3 is connected to the mutually connected sources of transistors Q1 and Q2, and the source and gate are connected to power supply VSS and reference voltage V REF , respectively.

In the circuit of FIG. 4, each output signal Vo1 and Vo
The second high level voltage Voo is approximately equal to the power supply voltage VCC. The low level voltage VOL of each output signal νo1 and νo2 depends on the impedance of transistors Q, Q2 and Q3. For example, when the input signal N1 is at a low level and the input signal VtN2 is at a high level, the transistor Q2 is on and the output signal Vo2 is at a low level. In this state, current flows from power supply Vcc to resistor R2 and transistor Q2. Power supply VSS through Q3
, and the potential of the output signal Vo2 is transferred to the transistor Q2. Q
3 and d depends on the impedance of resistor R2.

However, the MOS transistor Q2. which is generally turned on. The impedance of Q3 etc. increases as the temperature rises. This is the carrier mobility in the channel region (
This is because the higher the ambient temperature, the smaller the mobility. Therefore, as shown in FIG.
The low-level potential VOL of the output signal of the circuit shown in the figure increases as the ambient temperature T increases. That is, the conventional differential amplifier circuit has the disadvantage that the voltage level of the output signal fluctuates in response to changes in ambient temperature.

(Problems to be Solved by the Invention) In view of the problems of the conventional type described above, the present invention attempts to completely compensate or improve the temperature characteristics of the output signal of a differential amplifier circuit.

(Means for Solving the Problems) A differential amplifier circuit according to the present invention has a drain or collector connected to a power supply via a load, a gate or a gate receiving an input signal, and a source or emitter connected in common. It is basically constructed from a pair of differential transistors and a constant current source circuit connected to the commonly connected source or emitter circuit.

The constant current source circuit has a characteristic that the amount of current increases as the temperature rises by using, for example, the threshold characteristics of the transistor.

(Function) In the differential amplifier circuit, as mentioned above, the low level potential Vot of the output signal increases as the ambient temperature rises, but by using the above-mentioned means, the load Since it is corrected in the direction of increasing the current flowing through the
The potential of the output signal is stabilized against temperature changes.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a differential amplifier circuit according to an embodiment of the present invention. The circuit in the figure consists of a pair of N-channel MOS transistors Qi, Q2 whose sources are commonly connected, and load resistors R1, R.
N-channel MOS transistors Q3 p Q4 and P-channel MOS transistors Q5 . Q5, and resistors R3p and R4.

In the circuit of FIG. 1, the threshold characteristics of the P-channel MOS transistors Q5 and C6 of the constant current source circuit cs1 change as shown in FIG. rD increases.

In other words, the threshold voltage of the cell tends to decrease. Therefore, as the temperature rises, the current flowing through resistor R3 increases, and the current flowing through transistor Q4 also increases. Since the transistor Q4 and the transistor Q3 constitute a current mirror circuit, the current ISi flowing through the transistor Q3 also increases as the temperature rises. Therefore, the constant current source circuit CS1 increases the output voltage Vo of the differential circuit in accordance with the temperature rise.
1 and Vo2.

For example, considering the output voltage Vo2, since the voltage applied to the resistor R3 of the constant current source circuit C31 is equal to the threshold voltage Vth (P) of the P channel transistor Q6,
Therefore, the current flowing through the resistor R3 and the transistor Q4 is V
th(P)/R3. Therefore, the output voltage Vo2 is as follows.

Vo2 = Vcc-K ・Vth (P) ・R2/
R3-(11 here, K is 8 of transistors Q3 and C4
m ratio, K − gm (Q3) / gm (C4
). Therefore, the temperature change d of the output voltage Vo2
The change dVo2 with respect to T is as follows.

dT R3dT In equation (2), the ratio dVth (P)/dT is MO
In the case of an S transistor, it is constant at approximately 1.2 mV/'C, and it is also constant at an 8 m ratio, so the output voltage Vo2 can be set to any desired state by changing the resistance values of resistors R2 and R5. It becomes possible to make adjustments.

Note that the transistor Q5. of the constant current source circuit C31 in the circuit of FIG. Since Q6 constitutes a negative feedback circuit,
It is clear that the output current IS1 is not affected by fluctuations in the power supply voltage Vcc or the like.

FIG. 3 shows a differential amplifier circuit according to another embodiment of the invention. The circuit in the same figure is the P channel M in the circuit in FIG.
The OS transistor is replaced with a P N P type bipolar transistor, and the N channel MOS transistor is replaced with an N
This corresponds to a circuit replaced with a PN type bipolar transistor. The threshold characteristics of a PNP bipolar transistor, that is, the base voltage vs. collector current characteristics, are similar to those of a P-channel MOS transistor, and are also similar to those of an N-channel MOS transistor. In the circuit shown in the figure as well, the desired stabilized temperature characteristics can be obtained similarly to the circuit shown in FIG.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain an output current having a desired temperature coefficient according to the characteristics of the circuit and the conditions of use with a simple circuit configuration, and the differential amplification It becomes possible to completely achieve temperature compensation for each parameter of the integrated circuit device including the circuit and the differential amplifier circuit. In addition, since temperature compensation is performed using gate or base threshold characteristics, and such threshold characteristics are specific to the type of device such as a MOS transistor or a bipolar transistor, the temperature characteristics of the circuit are Variation is greatly reduced.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing a differential amplifier circuit according to one embodiment of the present invention, FIG. 2 is a graph showing characteristics of a P-channel MOS transistor, and FIG. 3 is a diagram showing differences in another embodiment of the present invention. FIG. 4 is an electric circuit diagram showing a dynamic amplifier circuit, FIG. 4 is an electric circuit diagram showing a conventional differential amplifier circuit, and FIG. 5 is a graph showing characteristics of the circuit shown in FIG. 4. Q, , Q2, Q3, C4: N channel MOS transistor, C5, C6: P channel MOS transistor, C7, C
6, Q9, C11O: NPN transistor, Q
ll, C12: PNP transistor, R,, R2
,..., R8: Resistor, A1: Differential circuit, C5I: Constant current source circuit. Figure 1 Figure 2

Claims (1)

[Claims] 1. A pair of differential transistors whose drains or collectors are connected to a power supply via a load, whose gates or bases receive an input signal, and whose sources or emitters are commonly connected;
1. A differential amplifier circuit comprising a constant current source circuit connected to a commonly connected source or emitter side, the constant current source circuit having a characteristic that the amount of current increases as the temperature rises. 2. The constant current source circuit includes a series circuit of a first P-channel MOS transistor and a first resistor connected between a high voltage side terminal and a low voltage side terminal of a power source, and a series circuit of a first P channel MOS transistor and a first resistor connected between a high voltage side terminal and a low voltage side terminal of a power source. A series circuit of a second resistor and a second P-channel MOS transistor connected between the terminal and the first resistor and the second P-channel MOS transistor, a P-channel MOS transistor whose gate is connected to the gate of the second P-channel MOS transistor to a connection point between the first P-channel MOS transistor and the first resistor; and a third and fourth P-channel MOS transistor.
MOS transistors, the third MOS transistor is inserted between the second P-channel MOS transistor and the low voltage side terminal of the power supply, and the fourth MOS transistor is connected to the common connection. 2. The differential amplifier circuit according to claim 1, wherein the differential amplifier circuit is inserted between a source and a low voltage side terminal of a power supply. 3. The constant current source circuit includes a series circuit of a first PNP bipolar transistor and a first resistor connected between a high voltage side terminal and a low voltage side terminal of a power supply, a second resistor connected between the terminal and the second PNP
a series circuit with a type bipolar transistor, the second
The base of the first PNP bipolar transistor is connected to the connection point between the resistor and the second PNP bipolar transistor, and the base of the second PNP bipolar transistor is connected to the first PNP bipolar transistor. and a current mirror circuit having a third and fourth bipolar transistor connected to a connection point with the first resistor, wherein the third bipolar transistor connects to the second PNP bipolar transistor and a low voltage of a power supply. 2. The differential amplifier circuit according to claim 1, wherein the fourth bipolar transistor is inserted between the commonly connected emitter and the low voltage side terminal of the power supply.