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# 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 (RL = -r22), the voltage gain becomes:

For a perfect buffer stage Rc + rc- rm = 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 RL = 15,000 ohms and Rg = 10 ohms,

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

VG = = .985

Under the conditions Rc + rc = rm (Rc = 12,000 ohms)

The maximum voltage gain

For the typical junction transistor, RL = 100,000 ohms, Rg = 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.

Last Update: 2007-09-12