Inverting input -> output-> V- and V+ (internal to opamp) -> ground.

If that is wrong, I don’t see how a voltage follower ever works, since the only connection of the inverting input is to the output.

The non-inverting inputs have no DC-path. A voltage follower doesn't work under this circumstance either.

 

I did not say anything about internal bias resistors. The output has one transistor to V+ and one to V-, which can never both be high impedance. I still don’t see why this is not a DC path to ground.

 

The op amps have no Vcc/2 bias voltage, the non inverting inputs are floating as there is no DC path anywhere. Only performing an AC sweep analysis is misleading as it doesn't show that the circuit doesn't really work as expected ;-).

I'm surprised you posted that circuit, which has no DC paths for both U1's and U2's (+) inputs.

You don't have a DC path to ground on the non-inverting inputs.

Yeah, my bad. That's what happens when you're rushing because DW is waiting to go out to garden centre...

I did do a transient check and it showed it was working ok. It wasn't until much later, after reading the comments, that I looked closer; it seems the LM324 library I was using (from Siemens I think) was a behavioural one that didn't care about little things like biassing. Swapping with a 'proper' TI library and it all goes badly wrong ... Lesson learnt!

And the trip to the garden centre cost me £600 for another, admittedly very nice, Japanese Maple (Acer P. "Garnet") to add to our growing collection of them

 

Don’t worry, we all have our “senior moments”.

We could open a new thread and make a long list of silly mistakes.

 

The output of the opamp?

That's going to in the inverting input.
It's the non-inverting (+) input that has no DC path for bias.

 

That's going to in the inverting input.
It's the non-inverting (+) input that has no DC path for bias.

Face slap. Sorry for the distraction. I was looking at the inverting input. Thank you for clarifying.