Post subject: PIN diode circutis no good at low frequencies?
Posted: Thu Oct 12, 2006 9:04 pm
Thu Oct 12, 2006 8:56 pm
Can someone please help
a novice understand why are PIN diode limiters, switches, attenuators
etc... never characterized or available for low frequency applications
(e.g. HF). What happens to make them no good down in that frequency
Post subject: Posted: Mon Oct
16, 2006 3:04 am
Joined: Mon Jun 27,
2005 2:02 pm
PIN Diodes are characterized only for RF/Microwave frequencies
because their resistance (In forward bias) is not constant at low
frequencies. Usually this resistance increases at low frequencies
(Below 10MHz) and is not stable with changing the forward current.
Hope this helps.
Post subject: PIN DiodesPosted:
Thu Oct 19, 2006 3:54 pm
Feb 22, 2006 3:51 pm
A bit more explanation
for "low frequency" use of PIN diodes:
PIN diode operation depends
on the carrier (hole or electron) lifetime in the intrinsic region.
The longer the lifetime, the lower the frequency you can use the
PIN diode at.
I've seen successful use of PIN diodes (with
the appropriately long carrier lifetime) in an attenuator operating
at 455 kHz. The designer had to search fairly hard for an adequate
The carrier lifetime depends on the purity
and defect density of the intrinsic region, so it's only somewhat
under manufacturer control. I haven't seen many PIN diode data sheets
that omit the lifetime as a spec - but if you're implementing a
circuit on an IC, the foundry may not know what a PIN diode will
do in their process, unless they've gone out of their way to characterize
When the signal cycle time T = 1/f is near the carrier
lifetime, the PIN diode starts acting like a regular diode.