SCts methods calculate the cascode amplifier

[Markie]

I read the lee's Rf circuits book, I am confused.

In ch7, hwo he can say that using short circuit time constants methods, what happens to the low-frequency gain if we take the following fig's Cin and Ce out of the circuit?

 

[mosheavi]

I used this configuration with npn transistors for AMP from DC - to 120Mhz 0-70v output.

So, you can take Ce and Cin out but you will have to take care for the DC Bias level - in temeperature etc.

The gain will be

G=Vout÷Vin ≈ Rd÷Re (from ≈ dc to fc)