From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-04-04 13:06:20
--- In buildcheapeeg_at_yahoogroups.com, "sleeper75se" <sleeper75se_at_yahoo.se> wrote:
> Current: +3.5mA/-2.5mA at 3kOhm/1000pF load.
> Propagation delay: (rise/fall) 1.25us/1.75us at this load.
A simple change increases the speed *and* lowers the current
consumption (how often does this happen? :-).
Replace the 10k resistors with 47k and add two 470pF (exact value not
critical) capacitors, one between the base of Q1 and the comparator
output, and the other between the base of Q3 and the comparator
output. (Schematic is updated...)
The capacitors work as shortcuts for the base currents during
switching, causing Q1 and Q3 to change faster and sooner,
significantly reducing the time when both transistors are conducting
simultaneously (which wastes current).
New data:
Current +0.5mA/-1.6mA at 3kOhm/1000pF load.
Propagation delay: (rise/fall) 300ns/200ns at this load.
http://groups.yahoo.com/group/buildcheapeeg/files/hardware%
20design/RS232TX/
Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:43 BST