TOP
BOTTOM
Why are we trying so hard to reduce resistance?
Resistance in the output path turns electrical energy into unnecessary heat.
Designers spend a lot time and effort removing as much heat as possible from
their systems, thus resistance is an unwanted parameter.
Why are we trying so hard to reduce inductance?
Inductance in the output path can cause voltage overshoot on the rising and falling
edges of the output pulse. The overshoot voltage is defined by the following
fundamental equation:
V = L * di / dt
Assume we wish to generate a 450 A pulse with a 1
µ
s rise time and a voltage
overshoot of less than 10 volts. What is the maximum allowable inductance in the
output path?
L = V / (di/dt) = 10 V / (450 A / 0.000001 s) = 22 nH
It is easily seen that with high currents and fast rise times, voltages can increase
rapidly if inductance is not kept as low as possible. While we are more concerned
about current overshoot than voltage overshoot, the overall result is that the
current pulse can be affected by undesirable inductance in the output path.
