The SERIES-NEGATIVE LIMITER limits the negative portion of the input pulse. The difference
between a series-negative limiter and a series-positive limiter is that the diode is reversed in the negative
A SERIES-NEGATIVE LIMITER with bias is the same as the series-positive limiter with bias,
but the outputs are opposite. When bias aids forward bias, only a portion of the negative input is removed.
When bias aids reverse bias, all of the negative and a portion of the positive input is removed.