JPH01807A - current mirror circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current mirror circuit, and particularly to a current mirror circuit suitable for calculating high frequency signals.

[Conventional technology]

A current mirror circuit is used to configure a current calculation circuit. For example, as the simplest calculation, a constant coefficient circuit is constructed by a current mirror circuit in which the emitter area ratio is adjusted to a desired coefficient. Such current mirror circuits are discussed in the book Bipolar and Moss Analog Inch Great Circuits by Graben.
Design, 1984. John Wiley Publishing, Chapter 4 (Grapen, "Bipolar and MOS Analog Integrated Circuits") (
A, B, Graben, Bipolar an
dMOS Analog Integrated C1
rcuits Design, 1984, John
Discussed in Wiley & 5ons, Cpt, 4).

[Problem that the invention seeks to solve]

The input side of the current mirror circuit is usually composed of one or more forward diode circuits. FIG. 2 shows an example of double rotation using a current mirror circuit. The input terminal 111 of this circuit is at a voltage higher than the reference (ground) voltage by 2VBB, where the base-emitter voltages of the transistors 151 and 152 are both VBE. Therefore, when the input voltage is Vz and each transistor is the same, the total emitter area of transistors 153 and 154 is twice that of transistor 151, so the output current Io is IO:211:2 (Vz 2VBE) /Rt, which depends on the voltage vB. For this reason, the voltage VIIE
When changes due to temperature etc., the output current I.

When used with a low signal source voltage Vl (especially low voltage in the high frequency range), the output current I.

There was a problem in that the changes in

The purpose of the present invention is to
It is an object of the present invention to provide a current mirror circuit that can perform calculations with high precision on input signals even at low voltages, especially high frequencies.

[Means for solving problems]

The purpose of the above is to insert a control circuit composed of a variable impedance circuit or a variable voltage circuit between the common terminal connecting the emitters of the input and output transistors and the ground, and when a voltage change at the input point occurs, the This is achieved by providing a negative feedback loop that cancels out changes in the input terminal voltage using the control circuit.

[Effect]

When the input terminal voltage changes due to temperature fluctuations or the like, the input terminal voltage of the control circuit changes due to the negative feedback circuit, thereby keeping the input terminal voltage of the current mirror circuit constant.

As a result, there is no fluctuation in the output current even when the input voltage is low, making it possible to perform highly accurate calculations.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In the same figure, the input terminal 11 of the current mirror calculation circuit 100
1 to 115 are connected to a signal voltage V via resistors R1 to R+s.
l ” V s is applied. Current mirror circuit 10
A negative feedback control circuit 200 is inserted between the 0 common terminal 105 and the input terminal 115. Negative feedback control circuit 20
0 is transistor 2 as a variable impedance element
20 and a differential amplifier 210. A reference voltage (not shown) as a target voltage of the input terminal 115 is applied to the reference input terminal 211 of the differential amplifier 210. The magnitude of this voltage is slightly higher than the voltage of the forward diode of the input terminal 115 of the current mirror arithmetic circuit 100, and the magnitude of the voltage is slightly higher than the voltage of the forward diode of the input terminal 115 of the current mirror operation circuit 100.
The value is about E.

In the above configuration, the negative feedback circuit 200 converts the voltage of the current mirror calculation circuit input terminal 145 into the amplifier 2
The current of the transistor 220 is adjusted so as to be equal to the voltage of the reference input 211 of No. 10. As a result, input terminal 1
Not only input terminal voltage 15 but also input terminal voltages 111 to 114 whose forward voltages are approximately equal are controlled to the same reference value. Therefore, if a voltage v6 approximately equal to the average value of the calculation input voltages 1 to V4 of the other calculation inputs 111 to 114 is applied to the input terminal 115, the calculation circuit 10
0 and output current Io do not depend on temperature fluctuations, etc.
1 = V 4 determined by Io = f (Vz, Vll
, Va, Va).

Here, various circuits can be considered as the current mirror arithmetic circuit 100, and it may be the double circuit described in FIG. 2. Another example is addition.

There are also subtractions, etc., and I will list them here.

FIG. 3 shows an adder circuit in which two current mirrors are connected in parallel. Current wire 1 and input terminal 11 from input terminal 111
The current flow 2 from 2 is added at the output terminal 130 as follows.

Io: Iz+Iz Figure 4 shows the same adder circuit, and input terminals 111° and 112 are 1.
The current mirror circuits are provided in parallel. The calculation formula is the same as that in FIG.

FIG. 5 shows an example of a subtraction circuit. Out crab 0 is Io:Ix
It becomes I2.

FIG. 6 also shows a subtraction circuit. The calculation formula is the same as that in FIG. 5, but since the circuit in FIG. 6 is composed of only NPN transistors, it can operate at higher speed than the circuit in FIG.

FIG. 7 shows an embodiment of the multiplication/division circuit. This circuit is
It consists of three current mirror pairs constituting an input stage and a differential pair of transistor output stages with fixed base voltages. The input currents flowing into each input terminal 111, 112, and 113 are It and Iz.

■3, and the output current of output terminals 130a and 130b is I
or, IO2, the following function holds true for each current: I 1/I 2I ot+
I02=I1 Therefore, the output current Ioz, Io2 is Iox=Iz/
(Lz+I3) ・IfI02=I3/ (I2+
I3) ・It becomes 11. This arithmetic expression is a limited power,
Although division is shown, this form is useful for application to brightness signal conditioning circuits in CRT display devices.

If the arithmetic circuit as described above is used as the current mirror arithmetic circuit 100 in FIG. Taking advantage of these characteristics, it becomes possible to operate at a low voltage of 5 V or less at 100 MHz, for example.

Next, another embodiment of the present invention will be described. FIG. 8 shows one embodiment, and the same or similar parts as in FIG. 1 are indicated by the same reference numerals. The circuit of FIG. 8 is a simple doubling coefficient as a current mirror operation circuit, and the transistors 155 and 156 of the output stage are 2 times the transistor 151 of the input stage.
It has twice the emitter area. transistor 153,
The circuit of 154 and resistor 175 constitutes an input terminal voltage detection circuit for obtaining a terminal voltage almost equal to the voltage at the input stage terminal against temperature fluctuations, etc. They are made up of transistors of the same type and size. Therefore, the voltage at terminal 115 is almost equal to the voltage at terminal 111, including temperature changes.

The voltage at the terminal 115 is applied to one input of the differential amplifier 210, and the other input is given a reference voltage VB by the voltage division of the resistors 176 and 177. amplifier 210
The output of the transistor 22 as a variable impedance element inserted between the common terminal 105 of the arithmetic circuit and ground
0 base electrode. Therefore, the voltage at terminal 115 ('': terminal 1
11) is equal to Va. Output 0 in that case
is Io:2 (VI Va)/R, and since Va does not fluctuate, it becomes a stable double coefficient circuit.

FIG. 9 shows another embodiment of the present invention, showing the main parts of a phase locked circuit. That is, the phase discrimination circuit 3
00 and its output switches 321 and 322, a filter consisting of a resistor 351 and a capacitor 350, and a current controlled oscillator (
emitter-coupled multivibrator) 160 and its constant current control circuit transistors 151 to 153. It is comprised of a bias constant current source 168, a current addition point control circuit 200, and the like. One purpose of the control in this circuit is to improve the control stability of one oscillator by controlling the voltage at the current inflow point 111 to always be equal to the voltage at the voltage division points of the switches 321 and 322. Therefore, additional points 11
The reference voltage to be controlled is given by voltage divider circuit transistors 221 and 222 having the same configuration as the output switches 321 and 322 of the phase discrimination circuit 300, respectively. By doing so, the voltage when the output pulses of the phase discrimination circuit 300 overlap can be made equal to the reference voltage, so that the overlap does not become an offset on the oscillator side.

The reference voltage of the addition point 111 is Vcc/2 or a ratio voltage of Vcc close to it. therefore,
In that case, amplifier 210 and its bias circuit include CMO
8 inverter amplifiers can also be used.

Although the present invention has been explained in detail by examples above, the present invention is not limited to the examples only, and can be applied to various circuits using current mirror circuits, MO3 circuits, MOS and bipolar composite circuits, etc. It is clear that it can be applied to formats.

[Effects of the Invention] According to the present invention, the current mirror circuit can be operated with high accuracy using a low voltage signal source.

This has the effect of realizing a highly accurate arithmetic circuit that operates at high frequencies.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of a conventional circuit, FIGS. 3 to 7 are partial circuit diagrams showing an application of the present invention, and FIGS. FIG. 9 is a circuit diagram showing other embodiments of the present invention. 6 100... Arithmetic circuit, 105... Common terminal, 111
~115...Input terminal, 210...Differential amplifier, 2
20...Transistor.

Claims (1)

[Claims] 1. Comparison means for detecting the difference between the voltage of one of the input terminals and a preset reference voltage, and a comparison means that is connected between the common terminal and the ground and that is connected to the one input terminal according to the output of the comparison means. 1. A current mirror circuit comprising voltage control means for controlling the voltage of the current mirror to be constant.