Tina-TI Basic Bridge amplifier appears to have only a gain of 2

Hi Lee,
Please note that in the TINA schematic you attached, there're two input sources. This will not work with AC analysis. You need to have one input source which goes into both amplifiers.
Regards,JC

Hi Lee,

        I've noticed that inputs to the amp on the left side are not biased to the same value of Vcc/2 I added two resistors R7 & R8 to correct this issue. Also the feedback loops needed to have a DC reference to bias the output. I have attached an schematic with the changes and the gain is approx 10dB which is close to the 20 V/V you where expecting.0841.Ceramic Speaker driver.TSC

Let me know if this helps,

Marcos

Hi JC and Marcos,

Marcos, your circuit looks the same as my image I posted but you are right, I somehow omitted the bias resistors from the input on the .TSC file.

I don't see the DC reference on the feedback loops you added??? The gain still seems to be around 6dB unless I'm doing something wrong. (or is the version you posted not the final version?)

JC. I don't quite understand. I only have the one source which is the voltage generator unless you're referring to the voltage pin. I can remove that as it serves no real purpose. I just added it as a measurement point but maybe that's a mistaken use of it.

Thanks for answering,
Lee.

Hi Marcos,

You are just running the AC Transfer Characteristics under AC Analysis?

Regards,
Lee.

Hi Lee,

        Yes that is the analysis I'm running. I will have to derive the transfer function of the circuit to know with certainty how to adjust the gain. You can infer some crude approximations from the circuit but I won't know for sure that I'm on the right track. Do you have the transfer function for this circuit handy? Or maybe some design guidelines?

Thanks,

Marcos

Hi Marcos,

Nothing so sophisticated as that. Just references from the web www.zen22142.zen.co.uk/.../lf071_mic.htm and an identical circuit which I can't find the reference to at the moment. When I run the simulation I am only getting 6dB gain on both your circuit and mine. Perhaps I am not correctly using TI TINA correctly as you managed 10 or so.

Probably the wrong place for this reference however it does have a transfer function.

http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCQQFjAA&url=http%3A%2F%2Fwww.rs-online.com%2Fdesignspark%2Fassets%2Fds-assets%2Fuploads%2Fknowledge-items%2Fpiezoelectric-audio-amplifiers%2FAppnotePAA-StepUpBTL-01.pdf&ei=O8xbVb7cN5KcygTj_4DADQ&usg=AFQjCNGZYAIWao8h-FJpkZDEIPZa9jlRHQ

 
Regards,
Lee.

Hi,

I'm just using the circuit in the Appnote PAA - StepUpBTL-01 from Sonitron. It is on this link with that exact circuit. www.sonitron.be/.../epag.php;hid=&subid=&eid=29

Regards,
Lee.

Thanks Kris,

What a silly mistake. I should invest in a new pair of glasses.

Regards,
Lee.