Question

A common base BJT amplifier at room temperature is connected with a resistance RC = 5 kΩ between VCC and the collector terminal, and the amplifier is driven by a signal source with an output resistance Rsig = 60 Ω. The designer would like the input resistance of the amplifier Rin to equal that of the signal source.

What is the resulting overall open circuit voltage gain Gv=vo/vs under this condition?
Assume alpha is approximately 1 and VT=25 mV. Provide your answer in V/V, rounded to one decimal place. Hint: draw the small signal schematic, and examine what would set the input resistance.

Answer 1

The overall open circuit voltage gain (Gv) of the common base BJT amplifier under the given condition is approximately -83.3 V/V.

Step-by-step explanation:

To determine the overall open circuit voltage gain (Gv) of the common base BJT amplifier, we need to consider the input resistance (Rin). Since the designer wants Rin to be equal to the output resistance of the signal source (Rsig), we can calculate Rin using the formula Rin = β * Rc, where β is the current gain of the BJT and Rc is the collector resistance. Given α is approximately 1, we can assume β = α.

In this case, the input resistance Rin equals 1 * 5 kΩ = 5 kΩ. To calculate the overall open circuit voltage gain Gv, use the formula Gv = -β * Rc / Rsig. Plugging in the values, we get Gv = -1 * 5 kΩ / 60 Ω ≈ -83.3 V/V.