Analysis of Common Base (CB) Amplifier using h-parameter: Figure 1 gives the basic circuit of a transistor (npn type) used as common base (CB) amplifier. In this case V_{s} is the signal voltage, V_{i} is the actual voltage at the input terminals and V_{0} is the output voltage.

Figure 2(a) gives the a.c. equivalent circuit obtained on having removed the dc source. On replacing the CB transistor by its small signal two generator h-parameter model we get the equivalent circuit of figure 1(b). Here also we assume sinusoidal input. Hence in the equivalent circuit of figure 2(b), we have used rms valued of voltages and currents namely I_{e}, V_{e}, I_{c} and V_{c}.

The equivalent circuit of figure 3 is similar that of the CE amplifier as shown in previous article Analysis of common emitter amplifier using h-parameter.

Hence analysis procedure is exactly the same. The expression of A_{I}, R_{i}, A_{V}, A_{IS}, A_{VS} and Y_{o }are therefore, the same as for CE amplifier except that h-parameter for CB configuration are used. Thus we get::

Current gain …..(1)

Input resistance ……(2)

Where

Voltage Gain …..(3)

Output admittance …..(4)

Overall voltage gain …..(5)

Overall current gain …..(6)

Power Gain ……(7)

Equations (1) and (7) may be used to calculated current gain etc. in term of CB h-parameter by corresponding CE h-parameters.

**Example 1: A transistor in CB configuration is driven by a voltage source V _{s} of internal resistance R_{s} = 1000. The load impedance is a resistor R_{L} = 4k. the h-parameters are : h_{ib} = 220, h_{rb} = , h_{fb} = – 0.98 and h_{0b} = . For this amplifier, calculate the current gain A_{I}, input resistance R_{i}, voltage gain A_{V}, overall voltage gain A_{VS}, overall current gain A_{IS} output resistance R_{0} and power gain A_{p}.**

Solution:

Current gain

Input impedance

Voltage gain

Overall voltage gain

Overall current gain

Output admittance

Hence M

Power gain