Transistor Basics is a free introductory textbook on transistors and their basic applications. See the editorial for more information....

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

transistor_basics_04-81.gif ;

this becomes. For the typical point-contact transistor, when RL = 15,000 ohms transistor_basics_04-82.gif and Rg = 10 ohms,


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

VG = transistor_basics_04-84.gif = .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