EL17 · Sem 4 · Analog circuits
Emitter follower (buffer)
Aim: Show that an emitter follower has gain ≈ 1 and low output impedance.
🧪 Live simulation🧊 Real-time 3D bench⚠ Simulated values, not physical measurements
🔬 Virtual lab
Starting the lab…
📘 Theory
The emitter follows the base minus about 0.65 V, so the voltage gain is nearly one, but the current gain is β. It is used to drive low-impedance loads without loading the previous stage.
Av ≈ RE / (RE + re) ≈ 1 · re = VT / IE
🧰 Apparatus (virtual)
- 12 V supply
- divider bias
- NPN
- 1 kΩ emitter resistor
- 1 V 1 kHz input
- oscilloscope
📝 Procedure
🎤 Viva questions
Why is it called a buffer
It isolates a weak source from a heavy load.
What is its phase shift
Zero: the output is in phase with the input.
🛡️ Safety
Virtual lab at safe low voltages. On a real bench: switch off before rewiring, check capacitor polarity, and never touch mains wiring without supervision.