Re: Amplify 1.5v DC to 5v DC?

mark.mcgee_at_csfb.com
Date: 10/21/04 

Date: 21 Oct 2004 02:04:54 -0700

Hi

I downloaded PSPICE, and simulated a couple of your suggested circuits.
Jon your first non-inverting circuit with the pair of transistors
NPN&PNP - I get the same results as you, using a DC sweep on the input
from 0v to 1.5v in 0.1v steps. Although, the IQ2 (IIRC) was negative -
is that what you'd expect because of the PNP transistor?

However, I can't get anything to happen with the later suggested
single transistor cct with the input at the emitter, and base held
permanently at 1.5v - I get the collector permanently sitting at 5v
across the whole input sweep. With or without a resistor on the
emitter and collector, both 47k as suggested.

Your fast switching, but inverting with three transistors, feed back(?)
and capacitors totally lost me I'm afraid. I'm interested to learn
what's going on here if you have the time to explain.

Speed wise, I don't think I need anything too fast - the clock pulse
duration is 1.25ms, I make that 800Hz, is that right? So nothing too
complicated/fast is required anyway.

I did find a couple of IC's yesterday for level shifting, but they are
14-pin and do additional stuff, which I don't really need. The IC's I
found were Texas Instruments CD40109B - CMOS Quad Low-to-high voltage
level shifter, and ON Semiconductor MC14504B Hex Level Shifter for TTL
to CMOS or CMOS to CMOS. The TI chip has enable pins in addition -
which I don't care about and can just fix enabled, but the ON looks
somehow simpler, but has this TTL/CMOS level switch configuration - I
think I need to configure it for TTL to CMOS for 1.5v to 5v level
shifting? Which do you prefer? Or can you suggest something simpler?
Cheers,
Mark