In pic7, I can't quite tell if the top transistor is an NPN or a PNP; assuming it's an NPN, there are two problems with the circuit. First, there is no pulldown resistor to allow its emitter to go negative; and second, there is no pullup resistor on the second transistor to allow its emitter to go positive.

In pic8, driving both the base and the collector with pure current sources gives no basis for establishing a defined operating point (Vce & Ic). If the circuit functions at all (as an amplifier, I assume), it will be by sheer luck.

The circuit in pic9 shows a proper base bias network and emitter ballast resistor to set the collector current, but with a pure current source feeding the collector the collector voltage is undefined.

 

In pic7, I can't quite tell if the top transistor is an NPN or a PNP; assuming it's an NPN, there are two problems with the circuit. First, there is no pulldown resistor to allow its emitter to go negative; and second, there is no pullup resistor on the second transistor to allow its emitter to go positive.

In pic8, driving both the base and the collector with pure current sources gives no basis for establishing a defined operating point (Vce & Ic). If the circuit functions at all (as an amplifier, I assume), it will be by sheer luck.

The circuit in pic9 shows a proper base bias network and emitter ballast resistor to set the collector current, but with a pure current source feeding the collector the collector voltage is undefined.

So, in pic8 whats wrong exactly? can we do something for "solve" it? or maybe its "ok"
And, in pic9, can we assume that circuit its ok?
Thank you!

 

So, in pic8 whats wrong exactly? can we do something for "solve" it? or maybe its "ok"

I told you what's wrong with it: the transistor's operating point is undefined. To fix it, re-design it so the operating point IS defined.

And, in pic9, can we assume that circuit its ok?

No, it is not OK, and I told you what's wrong with it.

 

I told you what's wrong with it: the transistor's operating point is undefined. To fix it, re-design it so the operating point IS defined.


No, it is not OK, and I told you what's wrong with it.

Thank you very much. Sorry for inconvenience.
Regards