[SOLVED] FEEDBACK compensation to ground?

[bowman1710]

Hi guys,

Quick question, on the attached file is a Intersil schematic, I'm looking at the FB and COMP pin in particular. If I'm correct in saying the FB pin is the negative leg of the amplifier and the COMP is the output of the amplifier. How come the compensation network is connected to ground? I've never seen it connected like this before.

 

[mtwieg]

Probably uses a transconductance error amplifier rather than a voltage amplifier. This is common in many control ICs.

 

[bowman1710]

Ok makes sense looking at it now, all the documents I have read/ had experience with have all used voltage amplifiers. Looks like I've opened another can of information I'll have to take in, seeing as I have no experience with transconductance error amplifier. Are there any pros/cons for using transconductance error amplifiers over voltage amplifiers?

 

[mtwieg]

One nice thing about the transconductance type is that the FB pin is actually a high impedance, which can simplify the design of compensation and feedback networks. Also since the COMP output is high impedance, you can override it with external circuitry easily.

Major con is that the transconductance may have a large tolerance to it.

 

[bowman1710]

Ok thank you for your help. Transconductance type doesn't seem all that different to be fair (in a sense of calcs etc) so i should be ok.