Common Base Amplifier Calculator Guide
Common-Base Amplifier
The common-base (CB) amplifier is a BJT configuration where the base is AC-grounded. It offers low input impedance and high voltage gain, commonly used for high-frequency applications.
Key Relations
- Voltage gain ≈ g_m R_C
- Input impedance ≈ 1 / g_m
- Transconductance: g_m ≈ I_C / V_T
Example
For I_C=2 mA, g_m ≈ 0.002 / 0.0257 ≈ 0.078 S. With R_C=4 kΩ, A_v ≈ 0.078 × 4000 ≈ 312.
FAQs
Why low input impedance?
The emitter sees a small-signal resistance ~1/g_m.
Use cases?
RF stages and impedance-level shifting.