TL026 with PWM for 10-bit ADC

Frank Li50498

Other Parts Discussed in Thread: TL026

Can I use TL026 as an input amplification stage for a 10-bit ADC and use PWM with RC filter to generate the gain control signal? Thanks.

over 12 years ago

0 Frank Li50498 over 12 years ago

Prodigy 40 points

The PWM is generated based on ADC output.

0 Ron Michallick over 12 years ago in reply to Frank Li50498

TI__Guru*** 139826 points

Hello Frank,

The AGC can be run from the filtered PWM signal.
Keep in mind the limited AGC range, Vref-180mV < Vagc < Vref+180mV.
This is shown in both figure 5 on page 4 and the 'Gain Characteristics' on page 5.

Regards,
Ron Michallick

0 Yan Li over 12 years ago in reply to Ron Michallick

Prodigy 50 points

Ron,

Thanks a lot for your answer. The Vg range is too small and doesn't fit the requirement. I have to check other parts.

Regards,

Yan

0 Yan Li over 12 years ago in reply to Ron Michallick

Prodigy 50 points

Ron,

I found SN7616666 and SN761643. Except the frequency range, they look perfect to my application. The signal I'm dealing with can be in the 10M~30M band and above 70MHz band. The datasheets of both parts have the AGC gain curve across 10MHz~100MHz. I wonder if these part can operate in 10MHz~30MHz band and above 70MHz band? Thanks a lot.

Best regards,

Frank.

0 Yan Li over 12 years ago in reply to Yan Li

Prodigy 50 points

Ron,

I also wonder if there is evaluation kit for SN761666 and SN761643. Thanks.

Best regards,

Frank

0 Ron Michallick over 12 years ago in reply to Yan Li

TI__Guru*** 139826 points

Yan,

These two device are not in my product line, but I looked at the data sheets.
The parts were designed with 30MHz to 70MHz in mind, but 10MHz to 100MHz is in the pass band per the data sheet charts.
These parts are a better choice than the TL026. The product page would mention an EVM board if one were available.

Ron

0 Yan Li over 12 years ago in reply to Ron Michallick

Prodigy 50 points

Ron,

I made an test board according to SN761666 data sheet. But I couldn't get it work. My signal is within 10M~30M range. MY schematics is as following. Can you point me to the right person or the right place to ask for checking this schematics. Thanks a lot.

Best regards,

Yan

0 Jim Karki over 12 years ago in reply to Yan Li

TI__Expert 4115 points

Yan,

I think I found the right contact person for this device and forwarded for comment. Please standby.

0 Yan Li over 12 years ago in reply to Jim Karki

Prodigy 50 points

Jim,

Thanks a lot for your help.

Best regards,

Yan

0 Jim Karki over 12 years ago in reply to Yan Li

TI__Expert 4115 points

From Hideo Nishi:

I regret to say there (is no longer) support (for) SN761666. Sorry for your inconvenience.

SN761766 is a simple GCA. Please check following items.

- Voltage of AGC-pin : AGC-pin has internal pull-down resister 100k ohm. This resister and R5 divide control voltage.

- Isolation between input signal and output signal : It happens undesired oscillation due to in/out interference.

- Connect GND1 and GCA2 lines at root of GND respectively, not to have common impedance.

Best regards,

Hideo Nishi

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TL026 with PWM for 10-bit ADC