JPS61148908A - Drive circuit - Google Patents

Abstract

PURPOSE:To improve the drive capability without attended with increase in a reactive current by providing a bias current supplementary circuit supplementing a bias current of a differential amplifier in response to an output rectifier current of the differential amplifier. CONSTITUTION:The bias current supplementary circuit 30 is added. The a current outputted from a collector of a transistor (TR)20 is fed to a base of a TR32, to which a current in response to an output current flows. The current is given to the base of TRs 14, 16 forming a differential amplifier 19 as a bias current via a current mirror circuit 35. That is, the bias current is added to a constant current from constant current sources 10, 12, the bias current flowing to the base of the TRs 14, 16 is supplemented Thus, the output current of the TRs 14, 16 is increased according to its bias current to improve the output drive capability of the output TR24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit suitable for, for example, a half-wave rectifier driver that operates at an extremely low voltage of 1 V or less.

[Conventional technology]

Conventionally, this type of drive circuit has been constructed as shown in FIG. That is, an AC input signal S is applied between input terminals 6a and 6b formed at the base of the transistor 2.4, and each transistor 2.4 changes its operating state every half wave of the positive and negative polarities of the AC signal S. Become. The collector of each transistor 2.4 is grounded, and a pair of constant current sources 10.12 is installed between its emitter and the positive line where the power supply terminal 8 is formed. It constitutes a bias power supply for transistors 14 and 16.

The emitters of the transistors 14 and 16 are connected in common, and a resistor 18 is installed between the emitters and the ground line. These transistors 14, 16 and resistor 1
A current mirror circuit consisting of a transistor 20 and a diode 22 is installed on the collector side of the transistor 14.16 as a load of the differential amplifier 19 constituted by the transistor 8.

An output is then obtained by the current from the collector side of the transistor 14.20, and this current output is added to the base of the output transistor 24 and rectified. An output terminal 26 is formed at the collector of the output transistor 24, a load 28 is connected between the output terminal 26 and the power supply terminal 8, and the output transistor 24 conducts every half wave of the AC input signal S. A drive current flows from the power supply terminal 8 to the load 28 through the output transistor 24, and the load 28 is driven.

In such a drive circuit, the differential amplifier 19 is composed of a transistor 14, 16 and a resistor 18, and
The load is configured with a current mirror circuit, and the level shift transistor 2.4 is installed at the input section, so
The voltage drop between the positive side line and the ground side line is low, and it can be driven by a power supply of 1 V or less, and stable operation can be guaranteed with, for example, a 1-inch battery.

[Problem that the invention seeks to solve]

However, in a drive circuit mainly using such a differential amplifier, in order to increase the output drive capability, it is necessary to increase the constant current 1o of the constant current source 10.12 or to decrease the resistance value R of the resistor 18. However, this setting has the disadvantage that the reactive current increases, the current consumption increases, and, for example, when the device is driven by a battery, its consumption increases.

Therefore, the present invention provides the following advantages:
This is intended to improve driving ability.

[Means for solving problems]

That is, the present invention provides a drive circuit that applies an AC input signal to a differential amplifier and forms a drive current in response to the output rectified current of the differential amplifier. A bias current supplement circuit is installed to supplement the bias current of the dynamic amplifier.

[For production]

Therefore, in the present invention, the bias current is supplemented in accordance with the output rectified current, and the bias current is supplied to the differential amplifier in accordance with the increase in the output current to be supplied to the load.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the drive circuit of the present invention, and FIG.
The same parts as the drive circuit shown in the figure are given the same reference numerals.

In FIG. 1, this drive circuit detects the output current of the differential amplifier 19 with respect to the drive circuit shown in FIG. A current replenishment circuit 30 is added.

In other words, this bias current replenishment circuit 30 has:
A diode 36 and a transistor 38 as well as a transistor 32 and a resistor 34 constitute a current source circuit 31 for forming a necessary bias current according to the output current taken out from the collector side of the transistor 14.20.
．． A current mirror circuit 35 consisting of 40 is installed.

The bases of the transistors 32 constituting the current source circuit 31 are commonly supplied with the output current that is applied from the collectors of the transistors 14 and 20 to the base of the output transistor 24. In this case, since the output current flows when the transistor 16 is conductive and the transistor 14 is non-conductive, it becomes a half-wave rectified current.

The current flowing through the transistor 16 passes through the transistor 20.32 and draws the base current of the diode 36 and the transistor 38.40, so a current corresponding to the current flows from the collector of each transistor 38.40 to each transistor 14.16. It is supplied to the base side, that is, the input side of the differential amplifier 19.

The operation of the above configuration will be explained.

When an AC input signal S is applied between input terminals 6a and 6b, transistor 2 becomes non-conducting on its positive polarity side and transistor 4 becomes conductive at the same time, transistor 2 becomes conductive on its negative polarity side, and transistor 4 becomes non-conductive at the same time. becomes. In this case, when transistor 2 is non-conductive, a bias current IO flows from the constant current source 10 to the base of transistor 14, and when transistor 4 is non-conductive, transistor 16
A bias current 0 is supplied to the base of the constant current source 12.

In the section where transistor 2 is conductive, transistor 14 is non-conductive, and at this time transistor 14.1
A current given in a half-wave rectified waveform flows from the collector side of the output transistor 24 to the base of the output transistor 24, and the transistor 24 becomes conductive due to this current. That is, a drive current given by a half-wave rectified output corresponding to the output current of the differential amplifier 19 flows through the output transistor 24, and the load 28 is driven by this drive current.

In this case, the current output from the collector of transistor 20 is applied to the base of transistor 32,
A current corresponding to the output current flows through the transistor 32.

This current flows through diode 36 and transistor 38.
Transistor 38.40 through a current mirror circuit of 40
is applied as a bias current to the base of transistor 14.16.

That is, this bias current is added to the constant current from constant current source 10.12, so transistor 14.16
The bias current flowing through the base of the transistor 14 and 16 is supplemented, and its current value increases in response to the large output when the output current of the differential amplifier 19 increases. The bias current increases in accordance with the bias current, and the output drive capability of the output transistor 24 is enhanced.

〔Effect of the invention〕

As explained above, according to the present invention, with an extremely simple configuration, the bias current can be increased only at the time of high output, and the efficiency (output drive capability) can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the drive circuit of the present invention, and FIG. 2 is a circuit diagram showing a conventional drive circuit. 19... Differential amplifier, 30... Bias current replenishment circuit, 31... Current source circuit, 35... Current mirror circuit.

Claims (2)

[Claims] (1) In a drive circuit that applies an AC input signal to a differential amplifier and forms a drive current in response to the output rectified current of the differential amplifier, the drive circuit generates a drive current in response to the output rectified current of the differential amplifier. A drive circuit characterized in that a bias current replenishment circuit is installed to replenish bias current. (2) The bias current replenishment circuit includes a current source circuit that forms the necessary bias current according to the output rectified current of the differential amplifier, and a current source circuit that supplies the bias current formed by the current source circuit to the differential amplifier. 2. The drive circuit according to claim 1, further comprising a current mirror circuit that supplies a current to the bias input side of the drive circuit.