JPS6042648B2 - temperature compensated amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a structure for reducing gain fluctuations due to temperature fluctuations in an integrated circuit.

That is, it uses the difference in temperature coefficient of resistance, for example, base diffusion resistance (2000 to 3500 ppm/℃)
The purpose of the present invention is to provide a temperature-compensated amplifier circuit that can reduce the fluctuation range of the amplifier gain with respect to temperature variables by utilizing the difference in temperature coefficient between the emitter diffusion resistance and the emitter diffusion resistance (400 to 700 ppm/° C.). A conventional amplifier includes transistors Q3 and Q, as shown in FIG.

Connect the emitters of and connect the resistors R4 and R5 to the collector.
Add a load of 3 and R with a base bias of 3. These transistors Q3 and Q constitute the differential amplifier circuit 100. A constant current was supplied to the emitter of the transistor from a constant current source formed by a transistor Q2 and a diode D3. The diode D8 further includes a transistor Q1 and a diode D1.
, D2 and resistors , , R2 supply a constant current from a constant current source to stabilize the voltage across the diode Da.
Supply voltage to this circuit from the power supply Vcc, apply a signal to the base of the transistor (from terminal a), and add the output obtained from the collectors of transistors Q and α to the next stage amplifier A to obtain an output from the terminal. In realizing such a conventional amplifier as a semiconductor amplifier, it is necessary to use a resistive resistor...a base diffused resistor that can obtain a relatively large resistivity as R6, that is, the base of the transistor. A resistor has been used that uses a region that is simultaneously diffused and formed during the formation diffusion process.

However, such a base diffused resistor has a relatively large temperature coefficient of resistance value, and has the disadvantage that the gain Aυ of the amplifier fluctuates greatly when the base-emitter voltage of the transistor and the forward voltage of the diode change with temperature. That is, the voltage gain Av of the differential amplifier circuit is determined by the conductance of the circuit Gn. , when the load resistance is RL, Av=G
m-RL. It is indicated by.

In the double-ended output format shown in FIG. 1 (that is, the format in which the output to the next stage is taken out from both differential transistors Q3 and Q4), Gr2
．． Shown by Chi. For single-ended output format, G
．． n = 100 yen. Here, q is the charge, k is Boltzmann's constant, T is the absolute temperature, and IO is the differential amplifier circuit 100.
, the collector current of transistor Q2. Since the transistor Q2 and the diode D3 constitute a current mirror circuit, the collector current of the transistor Q2 is substantially equal to the current flowing through the diode D2, that is, the collector current of the transistor Q1. Since the base current of transistor Q1 can be ignored, the collector current of the transistor is also the emitter current, and the current is (■BOOl+■BED2-VBEQl)/R
It becomes 2. In addition, ■BEDl9VBED2 is the voltage drop of the diode Dl, D2, VI3O,l is the transistor Q
The base-emitter voltage is 1. Therefore) 10:
(VBEDl+■BECl2-■BEQl)/R2. As a result, the ambient temperature Ta of the amplifier shown in FIG.
Voltage gain Avl at 25°C (Ta=25°C). teeth,
This is because RL=R4.

The temperature coefficient of the base diffusion resistance is, for example, +3500 ppm/°C, and the temperature coefficient of the base diffusion resistance of the diode and transistor is
For example, the temperature coefficient of emitter voltage is -2.0rn
V/°C, and considering that the ambient temperature of the amplifier has increased from Ta=25°C to +100°C, the base diffusion resistance is 1. The voltage between the base and emitter of the diode and the transistor (the diode normally uses the junction between the base and emitter of the transistor, so below is the voltage between the base and emitter of the transistor).
(treated in the same way as the emitter voltage) is 0.714 times, KT/q is 1.22 times, and the gain Aυ1 (Ta = 125°C) of the differential amplifier is , the gain is compared to the reference ambient temperature (Ta=25°C),
It becomes 0.57 severe and fluctuates greatly.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature-compensated amplifier in which the range of gain variation of the amplifier is greatly improved. According to the present invention, a first resistor is provided between the emitter of the first transistor and the reference voltage source, and a diode and a second resistor are provided between the base of the first transistor and the reference voltage source, The collector current of the first transistor is supplied to the emitter of a second transistor for signal amplification, and the first resistor is temperature-compensated by emitter diffusion of the transistor or an equivalent diffusion process. Get an amplifier.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a diagram explaining the present invention in detail. The differential amplifier circuit 100 and the next-stage amplifier A are the same as in FIG. A resistor R8 is inserted between the resistor R8, a diode D4 and a resistor R7 are inserted in series between the base of the transistor 9 and the positive pole of the power supply Vcc, and a resistor R7 is inserted between the base of the transistor α and the negative pole of the power supply Vcc. and a resistor R9.

These are formed on the same semiconductor chip. As the resistor R8, a resistor having a relatively small temperature coefficient of resistance value, such as a resistor separated from the island region (ie, epitaxial layer) of the semiconductor integrated circuit by double diffusion, is used. Typically, this is an emitter diffusion resistor that is formed at the same time as the emitter diffusion process of the transistor. The resistors and R9 must have the same temperature coefficient, and at least one of them must have a large resistance value, so they are formed in the island region of the semiconductor integrated circuit in a single diffusion process. A resistor is used. Typically, this is a base diffusion resistor that is formed at the same time as the transistor base diffusion process. Let us now consider the voltage gain of the amplifier shown in FIG.

The current source current of the differential transistors Q3 and Qi is the collector current of the transistor Q5, and this current is also the current flowing through the emitter resistor R8 of the transistor. Just a protest.
The voltage across the resistor R7 is equal to the sum of the voltage drop across the resistor R7 and the voltage drop across the diode D4, BED4, minus the base-emitter voltage BEQ of the transistor Q5. The voltage drop across resistor R7 is R, ?, where the power supply voltage is VCCl. 32110. Therefore, the resistance R
The current flowing through 8R7+R9, that is, the differential amplifier circuit 1
00 current source current 1.

(Collector current of transistor Q5) is ~[o:(■B
ED4-■BEQ5+R7I4l2ゝ50/
It becomes R7+R9R8.

Therefore, as described in the process of deriving formula 1 (formula), the second
The voltage gain Av2 (Ta=25°C) of the amplifier shown in the figure at the ambient temperature Ta=25°C is IX8.

The temperature coefficient of the base diffusion resistance is, for example, +3500 ppm.
/℃, the temperature coefficient of the emitter diffused resistance is, for example, +500
ppm/°C The temperature coefficient of the base-emitter voltage of a diode and a transistor is, for example, -2.0rT1V/°C, and now the ambient temperature of the amplifier is changing from Ta=25°C to +10°C.
Considering the case when the temperature rises by 0℃, the base diffusion resistance is 1.3
5 times, the emitter diffusion resistance is 1.0, and the voltage between the base and emitter of the diode and transistor is 0.7. Then, (VCCl-Vl3.D4) becomes 1.02 times, and the gain of the differential amplifier Aυ2 (Ta=1251C) is
VBED4: VBEQ5 is taken into consideration, and the gain is 1.0 compared to that at the reference ambient temperature (Ta=25°C). As described above, according to the present invention, temperature compensation of gain can be obtained by utilizing the difference in temperature coefficient of resistance, and fluctuations in gain can be reduced.

According to another embodiment of the present invention, as shown in FIG. 3, the emitters of the transistors Ql3 and Ql4 are connected together, and the collectors have resistors 6 and Rl7, and the signal applied to the terminal a'' is It is outputted from the collector, and in addition to being sent to the next stage amplifier A'', an output is obtained from the terminal b''.

The base bias of the transistor Ql4 is given by the resistor Rl9, and the transistor Ql3 obtains a constant voltage from the connection point between the diode Dl4 and the transistor Ql2 in the series circuit of the resistor t/LRl4, the transistor Ql2 diodes D, 4, D, 5, and the resistor Rl5. It is applied via resistor R2O. On the other hand, a constant voltage obtained from the connection point of diodes Dl4 and Dl5 is applied to the base of transistor Ql5, and transistor Q
A resistor Rl8, which is an emitter diffusion resistance, is added to the emitter of transistor Ql5, and a constant current is obtained from the collector of transistor Ql5.
It is supplied to the mutually connected emitters of transistors Ql3 and Ql4 of the differential amplifier circuit.

The collector of the transistor Ql2 generates a constant current, and the base thereof has a diode Dl3 and a resistor Rl. In order to guarantee the stability of the constant voltage, the series circuit of diode Dl3 and low resistor Rl2 includes transistor Qll, diodes Dll, Dl2, resistor Rll,
A constant current from a constant current source consisting of Rl3 is applied.
The entire structure is formed on one semiconductor chip. VCCl
l is the power supply. In Fig. 3, the ambient temperature Ta=
Transistors Ql3, Q of the differential amplifier circuit at 25°C
The gain Aυ3 (Ta=25°C) at l4 is the diode Dll, Dl2? The voltage drops of Dl39Dl5 are respectively VBEDll9VBEDl29VB! 11:Dl39■
The base-emitter voltages of BICDl5 to transistor Qll9Ql29Ql5 are respectively ■BEQll, VBO,
l2, ■BO, l5, the gain Aυ'' (Ta=25
℃) is given by.

q represents electric charge, k represents Boltzmann's constant, and T represents absolute temperature. The temperature coefficient of the base diffused resistance is, for example, +3500
ppm/℃, the temperature coefficient of emitter diffusion resistance is, for example, +5
00ppm/6C1 The temperature coefficient of the voltage between the diode and the transistor's base-emitter is, for example, -2.0rnv/
℃, and now the ambient temperature of the amplifier is from Ta=25℃ to +
Considering the case where the temperature rises by 100°C, the base diffusion resistance is 1.
A double, the emitter diffusion resistance is 1. Considering that the voltage between the base and emitter of the diode and the transistor is 0.7V, it becomes 0.741 times, and the gain of the differential amplifier Aυ
″(Ta: 1251C) is ~ ■ BEDl5: Ni ■ BEQ
l59VBEDl3:■BEQl2), and the gain is compared to the reference ambient temperature (Ta=25°C).
It becomes 0.944 times.

Therefore, compared to the conventional circuit shown in FIG. 1, the circuit according to the present invention has a gain variation due to temperature change of 1.66 times (2010g101.66=4.4dB).
It has been improved.

As described above, according to the circuit configuration according to the present invention, it is possible to realize a temperature compensated amplifier circuit that can reduce the fluctuation range of the gain of the amplifier with respect to temperature fluctuations.

Note that the present invention can be easily implemented even in an amplifier constructed using discrete components by using resistors with different temperature coefficients.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional amplifier circuit, and FIGS. 2 and 3 are circuit diagrams showing one embodiment and another embodiment of the present invention, respectively. Q1...Ql4 is a transistor, D1...
...Dl5 is a transistor, R1...R2O is a resistor, and A and A'' are the next stage amplifiers.

Claims (1)

[Scope of Claims] 1 A first transistor, a reference potential, a first resistor inserted between the emitter of the first transistor and the reference potential, a base of the first transistor and the a series circuit of a diode and a second resistor inserted between a reference potential; means for supplying current to the series circuit; a second transistor, means for supplying a signal to the second transistor, and a load connected to the collector of the second transistor, wherein the temperature coefficient of the first resistor is equal to the temperature of the second resistor. A temperature compensated amplifier characterized in that the coefficient is set smaller than the coefficient. 2. The first and second transistors, the first and second resistors, and the diode are formed on the same semiconductor chip, and the first resistor is a region in which impurities are doubly diffused in the semiconductor chip. Temperature compensation according to claim 1, wherein the second resistor is formed in a region formed by once diffusing impurities into the semiconductor chip. Amplifier with 3. The first and second transistors, the first and second resistors, and the diode are formed on the same semiconductor chip, and the first resistor is formed in a region formed simultaneously with the emitter diffusion of the transistor; 2. The temperature compensated amplifier according to claim 1, wherein said second resistor is formed in a region formed simultaneously with base diffusion of the transistor.