What is the impedance between the base of the BJT and ground of the common emitter amplifier circuit? The answer should be in terms of RE and hfe (the small current gain of the transistor). Is this a high or a low impedance (relative to the output impedance)?
Hint, this isn’t that bad remember the rules and the definition of hfe. Write down ΔIE in terms of ΔVB and RE then write down ΔIE in terms of ΔIB and hfe. Now the impedance looking into the base can be calculated from Ohms Law and by answering the questions what is ΔIB for a change ΔVB.