JPS6218806A - Current-voltage conversion circuit - Google Patents

Abstract

PURPOSE:To realize an attenuation circuit without any increase in current consumption and to reduce the current consumption of the whole circuit by providing a differential current switch circuit in a current mirror circuit which transmits a signal current. CONSTITUTION:When the DC voltage of a variable voltage source 17 which is impressed to based of one-side transistors (TR) 12 and 15 for current switches forming a differential couple constituting a differential current switch circuit D is much lower than the voltage of a DC bias power source 18 which is impressed to bases of the other-side TRs 13 and 14, those TRs 12 and 15 are on and the TRs 13 and 14 are off. Then, signal currents outputted from collectors of TRs 4 and 6 of the 1st and the 2nd current mirror circuits A and B are not transmitted to TRs 7 and 8 of the 3rd current mirror circuit C and no signal voltage is outputted at an output terminal 19. For the purpose, the voltage of the variable voltage source 17 is varied to vary the signal voltage obtained at the output terminal 19.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a current/voltage conversion circuit suitable for IC implementation.
In particular, the present invention relates to a current/voltage conversion circuit that converts a signal current into a signal voltage using a current mirror transmission means using an active load for the signal current.

[Conventional technology]

An example of a conventional current/voltage conversion circuit of this type will be described with reference to FIG. As shown in FIG. 2, this circuit consists of first and second current mirror circuits A and B including transistors 3 and 5, which serve as active loads for signal currents 1 and 2, and transistors 4 and 6 paired with each other. A third current mirror circuit C consisting of a pair of transistors 7.8 converts the difference component between the signal currents of the first and second current mirror circuits A and B into a third current mirror circuit C consisting of a pair of transistors 7.8.
to communicate. Then, after converting the difference component current of the signal current transmitted to the third current mirror circuit C into a voltage using resistors 9 and 10, this converted signal voltage is inputted to the attenuation circuit 20, so that the attenuation occurs. The signal voltage is attenuated according to the voltage applied to the control terminal 21 by the variable voltage source 22, and a predetermined output voltage is extracted from the output terminal 23. In this case, the attenuation circuit 20 is made of, for example, a differential transistor or the like, and the emitter current υ is varied by the voltage applied to the control terminal 21 to provide a predetermined attenuation. Note that 11 is a voltage source that generates the voltage required to drive the circuit.

[Problem that the invention seeks to solve]

However, in such conventional circuits, after converting the signal current into signal voltage using a current mirror circuit using an active load, the output voltage is obtained through an attenuation circuit, so the attenuation circuit requires extra current consumption. This is a factor that increases current consumption when converting to IC.

The present invention has been made in view of the above circumstances, and it is possible to reduce the current consumption by adding a circuit with an attenuation function to the current mirror circuit that transmits the signal current.
The purpose is to provide a voltage conversion circuit.

[Means for solving problems]

A current/voltage conversion circuit according to the present invention is a current/voltage conversion circuit that converts a signal current into a signal voltage by using a current mirror transmission means using an active load for a signal current, in which a transistor serves as an active load for each signal current. the first containing
and a second current mirror circuit, a third current mirror circuit that transmits a difference component between signal currents output from the first and second current mirror circuits, and the first and second current mirror circuits. a differential current switch circuit comprising a differential pair of current switch transistors inserted between each output terminal of the third current mirror circuit and each input terminal of the third current mirror circuit to turn on and off each current path; , an output means for converting a current accompanying a difference component of the signal current of the third current mirror circuit into a voltage, and applying the voltage to each of the current switch transistors forming a differential pair of the differential current switch circuit. The output voltage amplitude is made variable according to the bias voltage.

[Effect]

In the present invention, a differential current switch circuit is provided in a current mirror circuit that transmits each signal current, and a predetermined bias voltage is applied to each of the current switch transistors forming a differential pair of the differential current switch circuit. By doing so, the amplitude of the output voltage can be varied according to the bias voltage.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a current/voltage conversion circuit according to the present invention. This embodiment is different from the conventional example shown in FIG. In each current path between the respective collectors of transistors 7 and 8,
A differential current switch circuit is constructed of current switch transistors 12, 13 and 14, 15 forming a differential pair.

Here, in the differential current switch circuit, the emitters of transistors 12.13 and 14.15 forming a differential pair are common to transistors 4 and 6 that constitute first and second current mirror circuits A and B. connected to the collector.

Then, one transistor 12 and 1 forming a differential pair
5 has a collector grounded and a base connected in common, and a DC voltage is supplied to these bases as a bias voltage from a variable voltage source 17 via an attenuation control terminal 16. Further, the collectors of the other transistors 13 and 14 forming the differential pair are connected to the third current mirror circuit C.
The DC bias power supply 1 is connected to the collectors of transistors I and 8 constituting the
B), and the collectors of the transistors 8 and 14 are connected to a resistor 9. It is connected to the midpoint of the resistor 10 and outputs a predetermined output voltage from the output terminal 19. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Next, the operation of the configuration of the above embodiment will be explained.

First, the DC voltage applied from the variable voltage source 17 to the paces of the transistors 12 and 15 on one side of the differential pair through the control terminal 16 is equal to the voltage of the DC bias power supply 18 applied to the paces on the other transistors 13 and 14. If the voltage is high enough, these transistors 12.15 are off (
OFF), transistors 13 and 14 are both ON (O
N) The difference component between the signal currents 1 and 2 is outputted to the output terminal 19 as a signal voltage in exactly the same operation as in the conventional example described above.

Next, if the DC voltage of the variable voltage source 17 applied to the transistors 12 and 150 is sufficiently lower than the voltage of the DC bias power supply 18 applied to the transistors 13 and 14, these transistors 12.1
5 is on, transistors 13 and 14 are off,
The signal current outputted by the collectors of the transistors 4, 8 of the first and second current mirror circuits A, B) is not transmitted to the transistor 7.8 of the third current mirror circuit C.

Therefore, no signal voltage is output to the output terminal 19. Therefore, by changing the voltage of the variable voltage source 17, the signal voltage obtained at the output terminal 19 can be varied.

〔Effect of the invention〕

As described above, according to the present invention, an attenuation circuit can be realized without increasing current consumption by a simple configuration in which a differential current switch circuit is provided inside a current mirror circuit that transmits a signal current, and the overall circuit This has the effect of reducing current consumption.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a current/voltage conversion circuit according to the present invention, and FIG. 2 is a circuit diagram of a conventional example. 1.2...Signal current, 3-8...Transistor for current mirror, 9,10...Mechanism/resistance, 11...Voltage source, 12-15...Transistor for current switch , 16... Attenuation amount control terminal, 17... Variable voltage source, 18... DC bias power supply, 19... Output terminal, A-C... Current mirror circuit, D... ...Differential current switch circuit.

Claims (1)

[Claims] In a current/voltage conversion circuit that converts a signal current into a signal voltage using a current mirror transmission means with an active load for a signal current, first and second current mirror circuits each include a transistor serving as an active load for each signal current. , a third current mirror circuit that transmits the difference component of the signal current output from the first and second current mirror circuits, and a connection between each output terminal of the first and second current mirror circuits and the third a differential current switch circuit consisting of a current switch transistor forming a differential pair inserted between each input terminal of the current mirror circuit to turn on and off each current path; and the third current mirror circuit. and an output means for converting the current accompanying the difference component of the signal current into a voltage, and the output voltage amplitude is adjusted according to the bias voltage applied to each of the current switch transistors forming the differential pair of the differential current switch circuit. A current/voltage conversion circuit characterized in that the current/voltage conversion circuit is made to vary.