ece-1109 ECE-1109 Introduction to ECE
Comparison Table
| Parameter | BJT (Bipolar Junction Transistor) | JFET (Junction Field-Effect Transistor) |
|---|---|---|
| Device type | Bipolar — electrons + holes | Unipolar — majority carriers only |
| Control | Current-controlled (IB controls IC) | Voltage-controlled (VGS controls ID) |
| Input impedance | Low | Very high |
| Noise | Higher | Lower |
| Thermal behavior | Thermal runaway risk | Better thermal stability |
| Switching speed | Moderate | Faster (no minority-carrier storage) |
| Power handling | Higher | Lower |
| Linearity | Good | Better |
| Regions of operation | Cutoff, active, saturation | Cutoff, ohmic, saturation |
| Cost | Usually cheaper | Usually more expensive |
Advantages & Disadvantages
BJT — Advantages
- High current gain
- Good for power applications
- Works well with low-impedance inputs
- Strong gm at low voltages
BJT — Disadvantages
- Low input impedance
- Higher noise
- Thermal runaway risk
- Biasing more sensitive
JFET — Advantages
- Extremely high input impedance
- Very low noise
- Voltage-controlled (almost no gate current)
- Good thermal stability
- Faster switching
JFET — Disadvantages
- Lower power handling
- Harder to scale for high currents