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Rules of thumb - diode
- Diodes forward drop goes down as temperature goes up
- For a given current, the V/I curve shifts down by approximately 2 mV/°C.
- I = the net current flowing through the diode.
= "dark saturation current", or is the reverse bias saturation current
(or scale current) the diode leakage current density in the absence of
light. Is approximately doubles for every 10 °C increase in temperature - this temperature effect dominates the one in the exponent and results in the voltage drop with temperature. Is is related to the area of the junction and just how it was made.
- V = applied voltage across the terminals of the diode.
- q = absolute value of electron charge.
- k = Boltzmann's constant.
- T = absolute temperature (K).
- n = ideality factor, a number between 1 and 2 which typically increases as the current decreases.
- It is possible to pull the thermal voltage VT out of the
equation - VT is approximately 25.85 mV at 300 K, a temperature close to
"room temperature" commonly used in device simulation software. This
voltage you will see in
- But β increases with increasing temperature
Simplified trans-conductance of a Transistor
Transistor current ratios
- Doubling the collector current will cause an increase of about 18mv in Vbe or:
- Where ,
at room temperature