This document discusses the differences between LDMOS and bipolar technology, and compares their parameters and performances. LDMOS is a type of field effect transistor (FET) with advantages over bipolar junction transistors (BJTs) including thermal stability, frequency stability, higher gain, higher ruggedness, lower noise, lower feedback capacitance, simpler bias circuitry, constant input impedance, better IMD performance, lower thermal resistance, and better AGC capability.
This document provides a comparative study between Lateral Double-Diffused MOS (LDMOS) and Bipolar Junction Transistor (BJT) technologies for RF power applications. It analyzes key differences in their operating principles to determine suitability for specific use cases.
The text details the advantages of LDMOS technology, including superior thermal stability due to a negative temperature coefficient, higher gain at high frequencies, increased ruggedness against load mismatches, lower noise figures, and better Automatic Gain Control (AGC) capabilities. Conversely, it outlines the main drawbacks of LDMOS, such as lower power density resulting in higher costs per die area and susceptibility to electrostatic discharge damage.
| AGC range (typical) | 30 dB or better |
|---|---|
| Feedback capacitance ratio | 5 times lower than bipolar |
LDMOS has a negative temperature coefficient that turns the device off as it heats up, preventing thermal runaway, whereas bipolars have a positive coefficient.
The main drawbacks are lower power density, which leads to higher costs per die area, and susceptibility to damage from electrostatic discharge.