JPH0516767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amplifier circuit, and particularly to an amplifier circuit that converts an input signal voltage into a current and amplifies it.

[Conventional technology]

FIG. 2 is a circuit diagram of an embodiment of a conventional amplifier circuit.

This circuit uses the bases of differentially connected NPN transistors 9 and 10 (hereinafter transistors are referred to as Tr) as input terminals 3 and 4, respectively.
Constant current source 24 for each emitter of NPNTr9 and 10
The bases and collectors of NNPTrs 7 and 8, which are diode-connected in NNPTrs 9 and 10, respectively, are connected, and the emitters are connected to the high potential end 1 through resistors 16 and 17, respectively, and to the connection point of the base and collector of PNPTr 7. Connect the base of NPNTr11, connect the emitter of PNPTr11 to the collector of NPNTr15, connect the connection point to high potential end 1 via resistor 19, and connect the collector of NPNTr11 to the base of NPNTr15 and constant current source 25 ( The base of PNPTr12 is connected to the base-collector connection point of PNPTr8, the emitter of PNPTr12 is connected to the high potential end 1 via resistor 18, and the collector of PNPTr12 is connected to the collector of PNPTr12. Connect the base and collector of NPNTr13, and connect the base and collector of NPNTr13.
The base of NPNTr 14 is connected to the connection point of the collector, and the emitters of NPNTr 13 and 14 are connected to the low potential end 2 via resistors 20 and 21, respectively (hereinafter referred to as the lower output stage), and the emitters of NPNTr 15 and NPNTr 14 are connected to the low potential end 2 (hereinafter referred to as the lower output stage). It is an amplifier circuit consisting of a bias power supply 26 that connects the collectors of the NPNTrs 9 and 10, sets the connection point as the output terminal 5, and applies a bias voltage to the bases of the NNPTrs 9 and 10 through resistors 22 and 23, respectively. 5 is connected to a load 6.

[Problem that the invention seeks to solve]

In such a conventional current amplification circuit, the lower output stage is composed of a current mirror circuit of diode-connected NPNTr13 and NPNTr14.
The collector-base capacitance of No. 4 becomes a feedback capacitance and causes a gain drop at high frequencies. Therefore, peaking is applied to the frequency characteristics (characteristics) of the upper output stage, which consists of a current mirror circuit of diode-connected PNPTr7 and Darlington-connected PNPTr11 and NPNTr15, to compensate for the high frequency characteristics of the entire amplifier circuit. Therefore, a difference in gain occurs between the upper output stage and the lower output stage, resulting in uneven output current and distortion of the output signal. Furthermore, in the configuration of this amplifier circuit, when the current value of the constant current source 24 is fixed, the current value of the constant current source 25 must be fixed to an optimal value in order to equalize the currents in the upper and lower output stages. . In other words, since the emitter current of the output NPNTr 15 of the current mirror circuit that constitutes the upper output stage depends on the current value of the constant current source 25, if the current value of the constant current source 24 is changed to supply the necessary current to the load, the upper A difference occurs between the current conversion ratio of the output stage and the current exchange ratio of the lower output stage, and the output currents on the upper and lower sides become uneven, resulting in a difference in the amplitude of the AC signal between the upper and lower sides, which causes distortion of the output signal. Become. Therefore, in order to obtain the desired output current, it was necessary to change two constant current sources.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional technology, make the upper and lower output currents uniform, reduce the capacitance between the collector and base of the Tr, suppress the decrease in gain at high frequencies, and output It is an object of the present invention to provide a circuit with reduced signal distortion, and to obtain an amplifier circuit suitable for integrated circuits by reducing offset voltage and improving the relative ratio of resistances.

[Means for solving problems]

In the amplifier circuit of the present invention, the base of the first PNPTr is an inverting input terminal, the base of the second PNPTr is a non-inverting input terminal, and the emitter of the first PNPTr is connected to a high potential terminal via a first resistor. Connect and connect the first
The collector base of the third NPNTr and the base of the fourth NPNTr are connected to the collector of the PNPTr, and the collector base of the fourth NPNTr is connected to the collector base of the fifth NPNTr.
, the fifth collector is connected to the high potential end, the second and third resistors are connected to the emitters of the third and fourth NPNTr, respectively, and the fifth collector is connected to the high potential terminal.
The emitter of the PNPTr is connected to the high potential end through the fourth resistor, and the sixth resistor is connected to the collector of the second PNPTr.
Connect the collector base of the NPNTr to the base of the seventh NPNTr, connect the collector of the seventh NPNTr to the emitter of the eighth NPNTr, and connect the emitter of the eighth NPNTr to the collector base of the seventh NPNTr.
The connection point of the second and third resistors is configured as an output terminal at the collector of the NPNTr.

〔Example〕

Next, the present invention will be explained using the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. In this embodiment, amplifiers 39 and 40 having an inverting input terminal and a non-inverting input terminal are used, and the inverting input terminal of the amplifier 39 and the non-inverting input terminal of the amplifier 40 are connected. Connect the inverting input terminal, connect the bases of PNPTr11 and PNPTr12 to the outputs of amplifiers 39 and 40, respectively, and connect the emitter of PNPTr11 to the resistor 1.
9 to the high potential end 1, connect the collector and base of NPNTr28 connected to the diode to the collector of PNPTr11, connect the base of NPNTr29 to the collector and base of NPNTr28, and connect the emitter of NPNTr27 to the collector of NPNTr29. Then, connect the collector of NNPTr27 to the high potential end 1, connect the resistors 33 and 34 to the emitters of NNPTr28 and 29, and connect the collector of PNPTr27 to the high potential terminal 1.
Connect the emitter of NPNTr13 to the high potential end 1 through the resistor 18, connect the collector and base of NPNTr13 to the collector of PNPTr12, connect the collector and base of NPNTr13 to the base of NPNTr14, and connect the emitter of NPNTr30 to the collector of NPNTr14. Resistors 33 and 34 are connected to the collector of NPNTr 30, the emitters of NPNTr 13 and 14 are connected to the low potential end 2 via resistors 20 and 21, respectively, and the base of NPNTr 27 is connected to the intersection of the cathode side of diode 35 and resistor 36. , connect the anode side of the diode 35 to the high potential end 1, connect the other end of the resistor 36 to the base of the NPNTr 30 and the anode side of the diode 37, and connect the cathode side of the diode 37 to the anode side of the diode 38. The cathode side of the diode 38 is connected to the low potential terminal 2, and the collector of the NPNTr 30 and the resistor 3 are connected.
This is an amplifier circuit in which the connection point between 3 and 34 is configured as an output terminal 5, and the output terminal 5 is further connected to a load 6.

In the circuit of the present invention, the collector-base capacitance of NPNTr 14 of the current mirror circuit in the lower output stage becomes a feedback capacitance, which has been a problem in the past, by inserting NPNTr 30 into the collector of NPNTr 14. , an amplifier circuit with good frequency characteristics is obtained by reducing the feedback capacitance.

Further, by configuring the upper output stage circuit and the lower output stage circuit in the same circuit, it is possible to make the outflow current and the inflow current of the output current the same, thereby eliminating distortion of the output signal.

〔Effect of the invention〕

As described above, according to the present invention, an amplifier circuit with good frequency characteristics and low output distortion can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a circuit diagram showing an example of a conventional amplifier circuit. 1...High potential end, 2...Low potential end, 3, 4...
Input end, 5... Output end, 6... Load, 7, 8, 1
1, 12...NPN transistor, 9, 10, 1
3, 14, 15, 27, 28, 29...NPN transistor, 16, 17, 18, 19, 20, 2
1, 33, 34, 36...Resistance, 22, 23...
Bias resistor, 24, 25...constant current source, 35,
37, 38...diode, 39, 40... amplifier.

Claims (1)

[Claims] 1 The base of the first PNP transistor is used as an inverting input terminal, the base of the second PNP transistor is used as a non-inverting input terminal, and the emitter of the first PNP transistor is connected to a high potential terminal via a first resistor. , connecting the collector-base of a third NPN transistor and the base of a fourth NPN transistor to the collector of the first PNP transistor;
A fifth NPN transistor is connected to the collector of the fourth NPN transistor.
connecting the emitters of the fifth NPN transistor, connecting the collectors of the fifth NPN transistors to the high potential end, and connecting second and third resistors to the emitters of the third and fourth NPN transistors, respectively;
A fourth transistor is connected to the emitter of the second PNP transistor.
is connected to the high potential end through a resistor of the second
The collector-base of the sixth NPN transistor and the base of the seventh NPN transistor are connected to the collector of the PNP transistor, the emitter of the eighth NPN transistor is connected to the collector of the seventh NPN transistor, and the emitter of the eighth NPN transistor is connected to the collector of the seventh NPN transistor. The other ends of the second and third resistors are connected to the collectors of the NPN transistors, and the emitters of the sixth and seventh NPN transistors are connected to a low potential via fifth and sixth resistors, respectively. First and second bias power supplies are connected to the bases of the fifth and eighth NPN transistors, respectively.
An amplifier circuit characterized in that the connecting point of the resistors is configured as an output terminal.