Low Noise Device: FET

FETs (Field Effect Transistors) are considered low noise devices as they have a higher input impedance than BJT (Bipolar Junction Transistors) and are less sensitive to temperature changes. This makes them ideal for applications where low noise is important, such as in amplifiers, mixers, and oscillators.

Why FET is a low noise device?

1. Higher input impedance: FETs have a high input impedance due to the absence of a base current in the device. This leads to a lower noise figure as the input signal is not affected by the noise generated by the input circuit.

2. Less sensitive to temperature changes: FETs are less sensitive to temperature changes as the channel resistance is stable over a wide temperature range. This leads to a more stable device with less noise generated by the device itself.

3. Lower flicker noise: FETs have lower flicker noise compared to BJT as the noise generated by the device decreases as the frequency increases. This makes FETs ideal for low-frequency applications where flicker noise can be a problem.

Conclusion

In conclusion, FETs are a better choice when low noise is important as they have a higher input impedance, are less sensitive to temperature changes, and have lower flicker noise compared to BJT.