JPH0522059A - Gain controller - Google Patents

Abstract

PURPOSE:To miniaturize circuit scale and to reduce an influence caused by the dispersion of elements or a temperature characteristic by controlling the analog output signal level of a differential amplifier by controlling the power supply voltage of a digital buffer. CONSTITUTION:At a waveform generating circuit 1, differential pulse signals a and b, which phase is modulated, are outputted and inputted to a digital buffer 5. A power supply voltage VDO of the buffer 5 is set so as to be changed by a control signal Vs and as the result, the level of the pulse signal outputted from the buffer 5 is changed corresponding to the control signal Vs. Since the output signal of the buffer 5 is inputted to an integrator 3, turned to the signal of an analog waveform and inputted to a differential amplifier 7, the differential output signal level is changed corresponding to the level change of the inputted pulse signal. In this case, respective amplitude levels are changed between the signals of both differential outputs and concerning a DC level, however, relative relation is not changed between both the differential output signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gain control device suitable for converting a digital differential pulse signal into an analog output signal and controlling the level thereof.

[0002]

2. Description of the Related Art A digital differential pulse output signal (for example, PDM; Pulse Density Modulatio) from a waveform generating circuit.
n, PWM; Pulse Width Modulation) is output and converted into an analog output signal, and when the analog output signal level is controlled, the differential pulse output signal is input to the differential amplifier, and the differential is output by the gain control amplifier. The output signal level of the amplifier is controlled.

That is, as understood from FIG. 4, two differential pulse signals a, which are output from the waveform generating circuit 1,
b is input to the integrator 3 and becomes an analog waveform signal.

The output signal of the integrator 3 is input to the full-balance type gain control amplifier 10, and the signal level thereof is controlled by controlling the control signal V _S of the gain control amplifier 10.

[0005]

However, in such a circuit configuration, the double balance circuit 10A or the like is required, and the scale of the circuit configuration becomes large, and it is easily affected by the variation of the element and the temperature characteristic.

An object of the present invention is to provide a gain control device which can reduce the circuit scale and can reduce the influence of element variations and temperature characteristics.

[0007]

A gain control device according to the present invention includes a digital buffer 5 to which differential output pulse signals a and b output from a waveform generating circuit 1 are input.
And the integrator 3 into which the output signal of the digital buffer 5 is input and converted into the analog waveform output signals I and III, and the differential waveform output signals I and III of the integrator 3 are set as the desired analog output signal V. A differential amplifier 7, and in response to the power supply voltage of the digital buffer 5 being controlled,
The analog output signal V level of the differential amplifier 7 is controlled.

[0008]

In the gain control device according to the present invention, the analog output signal level of the differential amplifier is controlled by controlling the power supply voltage of the digital buffer.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a gain control device according to the present invention will be described below with reference to the drawings.

In FIG. 1, the waveform generating circuit 1 outputs differential pulse signals a and b (phase-modulated like PWM or PDM) and inputs them to the digital buffer 5.

The power supply voltage V _D0 of the buffer 5 is set so that it can be changed by the control signal V _S , and as a result, the height of the pulse signal output from the buffer 5 becomes the control signal V _S. Correspondingly changes.

Since the output signal of the buffer 5 is input to the integrator 3 and becomes an analog waveform signal, its differential output signal level changes in accordance with the change in the height of the input pulse signal. .

In this case, the amplitude level changes between the differential output signals, but the DC level does not change the relative relationship between the differential output signals.

That is, as understood from FIG. 2, the levels of the differential pulse signals of the waveform generating circuit 1 are from V _D0 to V _D0.
When it changes to _D1 , the differential pulse output signal of the buffer 5 changes from I and III to II and IV, respectively.

When the differential pulse output signals I and III are input to the integrator 3, the analog differential waveforms are respectively shown in FIG.
Waveforms I and III of the differential pulse output signal II, IV
Are the waveforms II and IV in FIG.

Next, the output signal of the integrator 3 is the differential amplifier 7
The DC potential is set by inputting to the differential amplifier 7
Then, since the differential input difference becomes the output, the waveforms I and II in FIG.
I becomes the waveform V, while waveforms II and IV become the waveform VI.

In this case, the points P ₁ and P _{2 at which} the waveforms I and III and the waveforms II and IV intersect are points at which the waveforms V and VI intersect, and the DCs also coincide.

Therefore, even if the power supply voltage of the buffer 5 is changed to change the height of the differential pulse, the output DC does not change, and only the amplitude is controlled.

As described above, in this embodiment, the output signal level of the differential amplifier 7 is changed by controlling the power supply voltage of the buffer 5 with the control signal V _S.

Therefore, the conventional double balance circuit 10A and the like are not required, so that the scale of the circuit structure can be reduced, and a stable device can be provided which is less affected by variations in each element and temperature characteristics. Becomes

[0021]

As can be understood from the above description, in the gain control device according to the present invention, the analog output signal level of the differential amplifier is controlled by controlling the power supply voltage of the digital buffer.

Therefore, since the double balance circuit is not necessary, the circuit scale can be reduced, and the influence of the element variations and the temperature characteristics can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a preferred embodiment of a gain control device according to the present invention.

FIG. 2 is a waveform diagram of differential output pulses and the like of the waveform generation circuit.

FIG. 3 is an output signal waveform diagram of an integrator.

FIG. 4 is an output signal waveform diagram of a differential amplifier.

[Explanation of symbols]

 1 Waveform generation circuit 3 Integrator 5 Digital buffer 7 Differential amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Miura 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (1)

Claim: What is claimed is: 1. A digital buffer into which a differential output pulse signal output from a waveform generation circuit is input, and an integrator into which an output signal of the digital buffer is input and converted into an analog waveform output signal. And a differential amplifier in which the differential waveform output signal of the integrator is the desired analog output signal, and the analog output signal level of the differential amplifier in response to the control of the power supply voltage of the digital buffer. The gain control device is characterized by being controlled.