| Author |
Message |
BasePointer
Joined: 03 Jul 2002
Posts: 113
Helped: 3
Location: TURKEY
|
 13 Nov 2004 21:18 Digital 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
Last edited by BasePointer on 14 Nov 2004 10:40; edited 1 time in total |
|
| Back to top |
|
 |
flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
|
| 13 Nov 2004 21:57 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.
|
|
| Back to top |
|
|
Hoko
Joined: 30 Oct 2004
Posts: 4
|
| 14 Nov 2004 2:34 Digital Gain Control |
|
|
|
| If you need a ADC finally. You can select a Delt-Sigma ADC with digitally controlled gain.
|
|
| Back to top |
|
|
nicleo
Joined: 06 Sep 2004
Posts: 717
Helped: 60
|
| 14 Nov 2004 4:34 Digital Gain Control |
|
|
|
[Option A]
Combine Operational Amplifier + 256-Step Digital Potentiometer
Dual-Polarity Amplifier is Controlled Digitally
http://pdfserv.maxim-ic.com/en/an/AN558.pdf
[Option B]
Programmable Gain Amplifier
PGA2310 (Stereo Audio Volume Control, with 8-bit gain control through SPI interface)
http://focus.ti.com/docs/prod/folders/print/pga2310.html
|
|
| Back to top |
|
|
BasePointer
Joined: 03 Jul 2002
Posts: 113
Helped: 3
Location: TURKEY
|
| 14 Nov 2004 10:39 Re: Digital Gain Control |
|
|
|
| nicleo wrote: |
[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 |
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
|
|
| Back to top |
|
|
nicleo
Joined: 06 Sep 2004
Posts: 717
Helped: 60
|
| 14 Nov 2004 13:59 Re: Digital Gain Control |
|
|
|
| BasePointer wrote: |
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.
|
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?
|
|
| Back to top |
|
|
BasePointer
Joined: 03 Jul 2002
Posts: 113
Helped: 3
Location: TURKEY
|
| 14 Nov 2004 16:52 Re: Digital Gain Control |
|
|
|
| nicleo wrote: |
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? |
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.
|
|
| Back to top |
|
|
nicleo
Joined: 06 Sep 2004
Posts: 717
Helped: 60
|
| 14 Nov 2004 17:36 Re: Digital Gain Control |
|
|
|
| BasePointer wrote: |
| 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. |
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?
|
|
| Back to top |
|
|
BasePointer
Joined: 03 Jul 2002
Posts: 113
Helped: 3
Location: TURKEY
|
| 14 Nov 2004 19:02 Re: Digital Gain Control |
|
|
|
| nicleo wrote: |
| 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? |
We are using ADE7758 from Analog Devices for our 3 phase active/reactive energy meters.
|
|
| Back to top |
|
|
metal
Joined: 21 Dec 2004
Posts: 366
Helped: 13
|
| 29 Dec 2004 5:43 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
|
|
| Back to top |
|
|
