JPH0369210B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a current inverting circuit, and particularly to a current inverting circuit with high frequency correction.

(B) Prior Art Generally, in audio circuits, etc., there are cases where it is desired to perform high frequency correction in the direction of cutting (suppressing) high frequency characteristics. High frequency correction in this sense
One way to do this inside an IC is to connect a Miller effect capacitor to a current inversion circuit that is often used inside an IC, as shown in FIG. This current inverting circuit consists of a pair of transistors Q1 and Q2.
Both bases of Q2 are directly connected, while the base and collector of transistor Q1 are commonly connected, and a capacitor C1 for high frequency correction is connected between the collector and base of transistor Q2.

(c) Problems to be Solved by the Invention In the conventional current inverting circuit described above, the impedance seen from point A to the transistor Q1 side is very low, so the mirror effect by capacitor C1 is difficult to take effect, and it is difficult to significantly cut out the high frequency range. For example, the capacitance of capacitor C1 must be made extremely large, but since a capacitor with a large capacitance cannot be accommodated inside the IC, sufficient high-frequency correction cannot be performed in the end.

The present invention has been made in view of the above-mentioned problems, and provides a current inverting circuit suitable for ICs that is capable of high frequency correction even if the capacitance of the Miller effect capacitor is relatively small. The purpose is to

(d) Means and operation for solving the problem In order to achieve the above object, the current reversing circuit of the present invention provides a current reversing circuit between the bases of a pair of transistors.
Connect two resistors whose resistance values are distributed to r and r/N in accordance with the current reversal ratio N, connect the connection point of both resistors to the collector of one transistor, and connect the collector of the other transistor. A capacitor for high frequency correction is connected between the base and the connection point of the two resistors.

In this current reversal circuit, the impedance of the base of one transistor is
In addition to rbb', resistors R1 and R2 are connected in series and become very large. Therefore, the time constant with the capacitor C11 becomes large, and as a result, the high frequency cut frequency becomes low, and a high frequency correction effect can be obtained without increasing the capacitor size.

(E) Examples The present invention will be explained in more detail below with reference to Examples.

FIG. 2 is a connection diagram of the current inversion circuit 11 showing one embodiment of the present invention. In the same figure, a pair of
Two resistors R1 and R2 are connected in series between the bases of NPN transistors Q11 and Q12, the collector of transistor Q11 is connected to the connection point B of resistors R1 and R2, and a high-frequency resistor is connected between the base and collector of transistor Q12. A correction capacitor C11 is connected. In addition, transistors Q11 and Q
12 emitters are connected to ground, and both collectors are connected to a current signal source 10 including a differential amplifier or the like.

Further, the resistors R1 and R2 are selected such that their resistance values are r and r/N, where N is the current reversal ratio of the circuit.

Current inversion circuit 11 connected and configured as described above
When a current I flows from the signal source 10 to the transistor Q11, a current NI corresponding to the current inversion ratio N flows to the transistor Q12.

Also, the impedance at point A is the transistor Q
In addition to the 11 resistors rbb', the resistors R1 and R2 are connected in series, so the resistor becomes very large. Therefore, the time constant with capacitor C11 becomes large, and as a result, the high frequency cut frequency becomes low, and even without changing the capacitance of capacitor C11, the high frequency correction effect can be obtained by connecting resistors R1 and R2. .

Note that in the current inversion circuit of the above embodiment, the capacitor C11 for high frequency correction is connected between the collector and base of the transistor Q12.
11 is the collector of the transistor Q12 and the resistor R
It may be connected between the connection point B of 1 and R2.

Further, the current inverting circuit 11 of the above embodiment includes a pair of
Although a case has been described in which the circuit is configured with NPN type transistors Q11 and Q12, it goes without saying that the present invention can also be applied to a current inverting circuit configured with PNP type transistors.

FIG. 3 is a connection diagram showing a current inversion circuit composed of PNP type transistors. Here, two current inversion circuits 21 and 31 connected to the signal source 20
However, except that the transistors Q21, Q22, Q31, and Q32 used are PNP type transistors, resistors R21, R22, and R31, R32
is connected between the collectors and bases of transistors Q22 and Q32, and high-frequency correction capacitors C21,
The basic configuration, such as connection of C31, is the same as that of the current inversion circuit 11 shown in FIG.

(F) Effects of the Invention According to the current reversal circuit of the present invention, two resistors whose resistance values are distributed according to the current reversal ratio N are connected to the base side, so that a capacitor for high frequency correction can be used. The impedance of the connected base side becomes high, and the high-frequency components can be cut out without increasing the capacitance of the capacitor, increasing the correction effect, so the capacitor needs only a small capacity, and it has a high-frequency correction function built into the IC. An optimal current reversal circuit can be obtained. Furthermore, since the two resistors are distributed according to the current reversal ratio, the accuracy of the current reversal ratio is improved.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of a conventional current inversion circuit with high frequency correction, Fig. 2 is a connection diagram of a current inversion circuit showing one embodiment of the present invention, and Fig. 3 is another embodiment of the present invention. FIG. 2 is a connection diagram of a current inverting circuit. 10, 20: Signal source, 11, 21, 31: Current inversion circuit, Q11, Q12, Q21, Q22, Q
31, Q32: Transistor, R1, R2, R2
1, R22, R31, R32: Resistance, C11, C
21, C31: Capacitor.

Claims (1)

[Scope of Claims] 1. In a current inverting circuit that includes a pair of transistors Q11 and Q12 and is connected to a current signal source 10, a current inversion circuit that corresponds to a current inversion ratio N is provided between the bases of the pair of transistors Q11 and Q12. Two resistors R1 and R2 whose resistance values are distributed as r and r/N are connected in series, and the connection point of both resistors R1 and R2 is connected to the collector of one transistor Q11, and the A current inverting circuit characterized in that a capacitor C11 for high frequency correction is connected between the collector and base of the transistor Q12 or the connection point between the two resistors.