Amp to drive 1ohm ribbon, using Dx

[tinitus]

Hi, I wonder, is this a cascode driver stage ?

[moschfet]

No, it is a darlington driver stage.

[juma]

Moschfet was faster

[wahab]

A little more than a darlington, it s a triple emitter follower.

Since there s no resistors on the emitter s of
the transistors that are in the middle of the arrangement,
the crossconduction range around the 0V crossing point
will be somewhat wider..

Also, the lack of this resistors make it imposible to discharge
the stored charges if even the transistor is driven to saturation,
wich is not a poblem in this case as they are fed from the same
supply voltage that their drivers, so they can t be driven to saturation.

[tinitus]

Apparently this one use one reversed output N device on output P side
Which is different ?

I wonder why there are no cascoded driver stage to find anywhere ?

[CBS240]

Q5/7 and Q6/8 are feedback pairs.

[Samuel Groner]

I wonder why there are no cascoded driver stage to find anywhere?

Because there is usually no point in adding a cascode... A cascode helps much for common-emitter stages, but typically far less for common-collector configurations. Input Z of these is more determined by load and hFE rather than Co and Early effect.

Samuel

[tinitus]

Originally Posted by Samuel Groner

A cascode helps much for common-emitter stages, but typically far less for common-collector configurations.

Ah, ok

And a cascode driver stage cannot be common emitter ?

[juma]

Originally Posted by wahab

A little more than a darlington, it s a triple emitter follower....

The question in post #1 was about driver stage, and it's just a Darlington (although, a poor one)

[wakibaki]

A cascode generally has the emitter of one device connected to the collector of a second, whereas in your first circuit the emitter connects into the base of the second.

Of course you can build the circuit with FETs, where it's source->drain, or valves, where it's cathode->anode.

Just because you see the devices stacked in this way, it does not necessarily mean that the circuit is a cascode.

As with most circuits, it's worth googling them and looking at wikipedia... cascodes are characterised by a high input impedance and high frequency response, the latter due to the minimisation of the effect of Miller capacitance.

w