Suggest me an amplifier that has digitally controlled gain

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BasePointer

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digital potentiometer circuits gain control

Hello,

I want to make 3 phases sine signal generator. I will use DDS from Analog Devices AD9833 for this. So I will be able to easily generate sine signals at frequency and phases that are desired. But also I should be able to adjust amplitudes of signals. So I'm looking for a amplifier that has digitally controled gain. It should be controlled with at least 8 bit. I'm waiting for your advices.

10x
BP
 

Re: Digital Gain Control

One method is to use the R-2R ladder network in the traditional DAC configuration with an op amp. Feed your sine wave as the input instead of the usual reference voltage.
 

Digital Gain Control

If you need a ADC finally. You can select a Delt-Sigma ADC with digitally controlled gain.
 

Digital Gain Control

[Option A]
Combine Operational Amplifier + 256-Step Digital Potentiometer

Dual-Polarity Amplifier is Controlled Digitally
**broken link removed**



[Option B]
Programmable Gain Amplifier

PGA2310 (Stereo Audio Volume Control, with 8-bit gain control through SPI interface)
https://focus.ti.com/docs/prod/folders/print/pga2310.html
 

    BasePointer

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Re: Digital Gain Control

nicleo said:
[Option A]

[Option B]
Programmable Gain Amplifier

PGA2310 (Stereo Audio Volume Control, with 8-bit gain control through SPI interface)
h**p://focus.ti.com/docs/prod/folders/print/pga2310.html
Click to expand...

PGA2310 is really good. But Its out can only supply 35mA. I need about 10W with low harmonic distortion. My final sine signal should be as pure as possible.

P.S. : My frequency range is from 40Hz to 120Hz.

10x
 

Re: Digital Gain Control

BasePointer said:
PGA2310 is really good. But Its out can only supply 35mA. I need about 10W with low harmonic distortion. My final sine signal should be as pure as possible.

P.S. : My frequency range is from 40Hz to 120Hz.
Click to expand...
We can add another high-current or high-power opamp, which configured as voltage follower, after the PGA2310. There are a few high-current opamp from Texas Instruments. For example:

OPA541
Power Supplies Up ±40V
Output Current Up to 10A


For low harmonic distortion, probably we should consider power audio amplifier. For example:
LM3886
High-Performance 68W Audio Power Amplifier
Output Current Up to 11.5A
exhibits extremely low THD+N values of 0.03%

Hope this will help. By the way, would you pls share what is the purpose of having such circuit?
 

    BasePointer

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Re: Digital Gain Control

nicleo said:
LM3886
High-Performance 68W Audio Power Amplifier
Output Current Up to 11.5A
exhibits extremely low THD+N values of 0.03%

Hope this will help. By the way, would you pls share what is the purpose of having such circuit?
Click to expand...

10x a lot Nicleo. I'm making a reference signal generator to calibrate our watt-hour meters. I will generate sensitive 3 phase voltage signals and their current signals then I will calibrate our energy meters by using it.
 

Re: Digital Gain Control

BasePointer said:
10x a lot Nicleo. I'm making a reference signal generator to calibrate our watt-hour meters. I will generate sensitive 3 phase voltage signals and their current signals then I will calibrate our energy meters by using it.
Click to expand...
That's a good project. Do you DSP for your watt-hour meter? Or, you use those energy ICs from Analog Devices to construct your watt-hour meter?
 

Re: Digital Gain Control

nicleo said:
That's a good project. Do you DSP for your watt-hour meter? Or, you use those energy ICs from Analog Devices to construct your watt-hour meter?
Click to expand...

We are using ADE7758 from Analog Devices for our 3 phase active/reactive energy meters.
 

Re: Digital Gain Control

Hello

To amplify the signal, I think TDA1552Q is a good choice, because it uses bridged amplifiers, so the signals to noise ratio is a lot smaller.

Regards
 

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