What is this symbol?

[macdonaldtomw]

What kind of amplifier is this? Why is it drawn with two non-inverting inputs, and why is its output connected directly to one of its non-inverting inputs?

This is from the TI 25148 datasheet

 

[FvM]

gm gain specification indicates an OTA amplifier type. It's often used in control amplifiers of power supplies. See e.g. https://en.wikipedia.org/wiki/Operational_transconductance_amplifier

Function of two non-inverting inputs needs explation, guess they are implementing a kind of min() funtion, soft start is overridng VREF.

 

[macdonaldtomw]

gm gain specification indicates an OTA amplifier type. It's often used in control amplifiers of power supplies. See e.g. https://en.wikipedia.org/wiki/Operational_transconductance_amplifier

Function of two non-inverting inputs needs explation, guess they are implementing a kind of min() funtion, soft start is overridng VREF.

Thanks!

Looks like perhaps the non-inverting input that is connected to the amplifier output is the one that is providing the input bias current that controls the aplifiers' transconductance. The datasheet states that the amplifier has a constant transconductance so maybe that is achived by tying the input bias pin to the output... not sure.

 

[dick_freebird]

Seems like a floor + demand kind of setup. The text features may
be corrupted by the fine folks in MarCom (marketing "communcations").
The "connection" to soft start that is shown as a short may in fact be
multiple branches, not a short, "obscured for clarity". Heh.

I know in my POL chip designs I always found it necessary to clamp
the error amp input -and- output to flatten any early "activity" while
power is ramping. UVLO-> SS -> Error -> PW.