JPH04348605A - Amplifier and detection circuit - Google Patents

Abstract

PURPOSE:To prevent an output signal level from being subject to drift due to temperature by applying temperature compensation to the circuit amplifying and detecting an electric signal and outputting the result. CONSTITUTION:A power supply voltage is divided by a resistor R1 and a series circuit comprising a diode D3 and a resistor R2 toward ground and the divided voltage is inputted to a base of a transistor(TR) Q1, its collector connects to ground and an input signal is fed to a base. Then power is supplied to the emitter via a resistor R3, an output is extracted from its emitter and inputted to an anode of a diode D4, its cathode is connected to ground via a capacitor C2, a detected voltage is extracted across the capacitor C2 and fed to a base of the TR Q2. Power is supplied to the collector via a resistor R4 and the emitter is connected to ground via a resistor R5, an output is extracted from the collector. Same type of components are employed for the diodes D3, D4 and complementary TRs are adopted for the TRs Q1, Q2 to attain temperature compensation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit that amplifies and detects electrical signals and outputs them.

0002

[Prior Art] Conventionally, an amplification and detection circuit as shown in FIG. 2 has been used, in which 11 is a B power supply;
A driving power is supplied from 1 to the collector of a transistor 14 via a resistor 12, the emitter of the transistor 14 is connected to ground, and an amplitude modulated wave signal is applied to the base of the transistor 14 via an input terminal 13. is amplified and outputted by the transistor 14, and the output is taken out from the collector of the transistor 14 and connected to the detection diode 15.
Insert the capacitor 16 between the cathode of the diode 15 and the ground, and connect the capacitor 16 to the anode of the diode 15.
The detection output generated at both ends of the signal is inputted to the base of a transistor 18 used as an amplifier in the next stage for signal processing. However, the diode 15 and the transistors 14 and 18 have temperature characteristics, and as the temperature of the transistor increases, the forward voltage between the base and emitter decreases, and similarly, the forward voltage between the anode and the cathode of the diode decreases. decreases, so transistor 18
This resulted in the signal level output from the device drifting due to temperature.

0003

SUMMARY OF THE INVENTION An object of the present invention is to perform temperature compensation on an amplification and detection circuit to suppress temperature-induced drift of the output signal level.

0004

[Means for Solving the Problems] FIG. 1 is an electrical circuit diagram of a temperature-compensated amplification and detection circuit showing one embodiment of the present invention. The voltage is divided by the resistor R1 and the second resistor R2 connected to the ground side, and the divided voltage is input to the base of the first transistor Q1, which is used as an amplifier, and the input signal is added to the base. The power supply voltage Vcc is supplied to the emitter of the first transistor Q1 via the third resistor R3, the collector is connected to the ground, and the output is taken out from the emitter and inputted to the anode of the first detection diode D4. The cathode of is connected to ground via a charging/discharging capacitor C2, and the detected output is taken out from both ends of the capacitor C2 and input to the base of a second transistor Q2 which is used as an amplifier in the next stage. Q2
The power supply voltage Vcc is supplied to the collector of the second transistor Q2 through the fourth resistor R4, and the emitter of the second transistor Q2 is connected to the ground through the fifth resistor R5.
In the amplification and detection circuit which extracts the output from the collector of the first transistor Q1, a second diode D3 is inserted into the base circuit of the first transistor Q1, and the anode side of the diode D3 becomes the base side of the first transistor Q1. , the second resistor R in series with the diode D3.
2, the base of the first transistor Q1 is grounded, the first diode D3 and the second diode D4 are of the same type, and the first transistor Q1 and the second transistor Q2 are complementary types. temperature compensation.

[0005]

[Operation] With the above-described configuration, the present invention amplifies and detects an input signal and outputs it. Temperature compensation is performed to prevent temperature drift in the level of the signal output from the amplification and detection circuit with respect to the input signal. is being carried out. In FIG. 1, transistors Q1 and Q2 are complementary types, diodes D3 and D4 are of the same type, and the resistance values of resistors R1 to R5 are set to R1 to R5.
5, the current flowing through resistor R2 is Ia, the current flowing through resistor R3 is Ib, and the current flowing through diode D4 is Ic.
, the current flowing through resistor R5 is Id, and Ia≒Ic, I
Let b≒Id. Transistor Q1 and transistor Q
The forward voltage between the base and emitter of 2 is V1eb, respectively.
, V2eb and diode D3 and diode D4
Assuming that the forward voltages of are respectively V3 and V4, and the drift of the transistor and diode when the temperature changes is as follows, Forward voltage drift between the base and emitter of transistor Q1: △V1eb Base and emitter of transistor Q2 Forward voltage drift between: △V2eb Forward voltage drift of diode D3: △V3 Forward voltage drift of diode D4: △V4

The base potential V1b of the transistor Q1 is [Vcc
−(V3+△V3)]×R2/(R1+R2)
+(V3+△V3) The emitter potential V1e of transistor Q1 is [Vcc -(V3+△V3)]
×R2/(R1+R2)+(V3+△V3)+(V
1eb+△V1eb) Base potential V of transistor Q2
2b is V1e-(V4+△V4) Since Ia≒Ic, V3≒V4, △V3≒△V
4 Therefore, V2b=[Vcc −(V3+△V3)]
×R2/(R1+R2)+(V1eb+△V1eb)
The emitter potential V2e of the transistor Q2 is V2b-(V
2eb +△V2eb) Since Ib≒Id,
V1eb ≒V2eb, △V1eb ≒△V2eb
V2e= [Vcc - (V3+△V3)]
×R2/(R1+R2) The collector potential V2c of transistor Q2 is V2c=
Vcc - (R4/R5) x V2e
= Vcc - (R4 / R5) x R2
/(R1+R2)×[Vcc −(V3+△V3)] The fluctuation △V2c of the output voltage of transistor Q2 is △V2c=
(R4/R5)×R2/(R1+R2)×△V3 Therefore, if (R4/R5)×R2/(R1+R2)≪1, then the temperature drift of the signal output from output terminal 2 can be expressed as the forward voltage of the diode. drift can be suppressed to below.

[0007]

[Embodiment] Fig. 1 is an electrical circuit diagram of an amplification and detection circuit with temperature compensation, showing an embodiment of the present invention. The signal is input to the base of a transistor Q1 used as an amplifier via a capacitor C1. The base of the transistor Q1 is connected to the power supply voltage Vcc via a bleeder resistor R1, and is further connected to a diode D3.
The base of the transistor Q1 is grounded by the resistor R2 connected in series with the transistor Q1, and the anode side of the diode D3 becomes the base side of the transistor Q1.The power supply voltage Vcc is divided and the divided voltage is biased to the base of the transistor Q1. It is added as a voltage.

The emitter of the transistor Q1 is connected to the power supply voltage Vcc through a resistor R3, the collector is connected to ground, and the output is taken out from the emitter and inputted to the anode of a detection diode D4.
The cathode of the transistor Q2 is connected to the ground via a charging/discharging capacitor C2, and the detection output is taken out from both ends of the capacitor C2 to be used as the next stage amplifier.
is entered on the basis of The collector of the transistor Q2 is connected to the power supply voltage Vcc through a resistor R4, the emitter of the transistor Q2 is connected to ground through a resistor R5, and the output is taken out from the collector of the transistor Q2. Diode D3 and diode D
4 are of the same type, PNP and NPN complementary types are used for transistors Q1 and Q2, the currents flowing through diode D3 and diode D4 are made almost equal, and resistors 3 and 5 are of the same type. Temperature compensation is achieved by making the flowing currents approximately equal and making the resistance values of each resistor used in the circuit satisfy the following equation. (R4/R5)×R2/(R1+R2)≪1

0
009]

[Effects of the Invention] As explained above, according to the present invention,
Temperature compensation can be performed by using diodes of the same type and complementary transistors in the amplification and detection circuits, and it is possible to provide an amplification and detection circuit that suppresses output drift due to temperature changes in the amplification and detection circuits. can.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram of an amplification and detection circuit with temperature compensation showing an embodiment of the present invention.

FIG. 2 is an electrical circuit diagram of an amplification and detection circuit showing a conventional example.

[Explanation of symbols]

1 Input terminal 2 Output terminal R1 Resistor R2 Resistor R3 Resistor R4 Resistor R5 Resistor C1 Capacitor C2 Capacitor D3 Diode D4 Diode Q1 Transistor Q2 Transistor Vcc power supply 11 Power supply 12 Resistor 13 Input terminal 14 Transistor 15 Diode 16 Capacitor 17 Power supply 18 Transistor 19 Resistor

Claims (2)

[Claims] Claim 1: A power supply voltage is divided by a first resistor and a second resistor connected to the ground side, and the divided voltage is inputted to the base of a first transistor used as an amplifier, and the first A power supply voltage is supplied to the emitter of the transistor through a third resistor, the collector is connected to ground, the output is taken out from the emitter and inputted to the anode of the first diode for detection, and the cathode of the diode is used for charging and discharging. Connect it to the ground via a capacitor, take out the detection output from both ends of the capacitor, input it to the base of the second transistor used as the next stage amplifier, and connect it to the collector of the second transistor via the fourth resistor. In the amplification and detection circuit, the base of the first transistor is supplied with a power supply voltage, the emitter of the second transistor is connected to ground through a fifth resistor, and the output is taken out from the collector of the second transistor. A second diode is inserted into the circuit so that the anode side of the diode becomes the base side of the first transistor, and the base of the first transistor is grounded with the second resistor connected in series with the diode. 1. An amplification and detection circuit characterized in that the first diode and the second diode are of the same type, and the first transistor and the second transistor are complementary types for temperature compensation. 2. The amplifier according to claim 1, wherein currents flowing through the first diode and the second diode are approximately equal, and currents flowing through the third resistor and the fifth resistor are approximately equal. and detection circuit.