Voltage Gain in the Grounded Collector Connection

Author: Leonard Krugman

The voltage gain, as defined in equation 3-24 by the general four-terminal parameters is:

Under the conditions for infinite input resistance and infinite current gain (R_L = -r₂₂), the voltage gain becomes:

For a perfect buffer stage R_c + r_c- r_m = 0. Thus, the voltage gain equation becomes

The maximum voltage gain as defined by equation 3-25 is

;

this becomes. For the typical point-contact transistor, when R_L = 15,000 ohms and R_g = 10 ohms,

Under the conditions R_L = -r₂₂ = 11,850 ohms

VG = = .985

Under the conditions R_c + r_c = r_m (R_c = 12,000 ohms)

The maximum voltage gain

For the typical junction transistor, R_L = 100,000 ohms, R_g = 10 ohms

The maximum voltage gain

Notice that in all of the above cases, the voltage gain is slightly less than unity. This is typical of the grounded collector connection.