is this one a buffer ckt help ?

[ajays2539]

please help ,,what this ckt work ?

 

[BradtheRad]

The left-hand circuit inverts the signal, at very high gain. When the input is above 2.5V (approx.), the output goes low. The rest of the time the output is high (near supply V).

The right-hand circuit is a non-inverting buffer, in simple terms. However the output does not necessarily go to the supply rails. The output volt levels depend on individual mosfet response.

 

[Audioguru]

The pair of IGBTs on the left side will probably draw a very high "shoot-though" current when they switch, but their voltage loss is very low. It is an inverter.

The pair of IGBTs on the right side will have a wide input voltage dead band causing severe crossover distortion and will have very high voltage losses.
It does not invert.

 

[ajays2539]

The pair of IGBTs on the left side will probably draw a very high "shoot-though" current when they switch, but their voltage loss is very low. It is an inverter.

The pair of IGBTs on the right side will have a wide input voltage dead band causing severe crossover distortion and will have very high voltage losses.
It does not invert.

yes 2nd will not invert but ,,its a non inverting buffer ?

 

[Audioguru]

The 2nd circuit has the IGBTs turned off most of the time because the gates are connected together so that the IGBTs conduct only at high peak signal voltages. Then it is not linear.
I think a buffer should be linear.

 

[BradtheRad]

yes 2nd will not invert but ,,its a non inverting buffer ?

The term 'buffer' implies the output signal resembles the input.

However my simulations show the right-hand circuit can't be called a buffer. The output does not go to 0V ground, that is, not in any definite manner.

I suggest you try running a few simulations on the right-hand circuit. Try a variety of supply V, and input signals, and mosfet parameters, etc.

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The bottom P-mosfet will sink current. In that sense it provides a path to 0V ground. But what would you measure with a voltmeter? Its unpredictable, since it depends on individual mosfet characteristics.