Hi AAC -

I'm looking at circuit 16 in Texas Instruments AN-20, http://www.ti.com/lit/an/snoa621c/snoa621c.pdf.

The circuit uses two large capacitors at the input and, in the notes, it states that this is the difference between the circuit functioning as an "Absolute Value Generator" and a "Full-Wave Rectifier."

Could someone explain the difference to me?

Also, the offsets seem very large on the non-inverting inputs. I'm not sure if anyone has experience with the LM107 in contrast with the TL074 - but is it possible that modern op-amps don't require that kind of compensation?

Thanks.

 

Fig. 16. Photovoltaic Cell Amplifier
This isn't working. Please clarify.
Yes. I was there for the LM101. Offset voltage has improved quite a bit since then.

 

Sorry, it's circuit 16 - in the table of contents... it's figure 25.

 

If you short out C1 then this full wave rectifier will respond to any DC level at the input. With the capacitor, it's a full wave rectifier of the AC signal. Without the capacitor it's still a full wave rectifier, but it will include any DC component in its activities.