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You need a resistor in series with the base (see Mike ML's circuit). Otherwise you could zap the transistor.I was trying to do this with an NPN BJT, 3.3v signal IN to base, emitter to GND, collector to 10k resistor to +5v, then reading the signal from the collector. I must have screwed up.
MikeMl said:2n3904, 10K base resistor, 4.7K pull-up to +5V.
unclejed613 said:the level shifter shown within the dotted box is for a 3.3V OC output (with or without a pullup). for active outputs, you can simplify it by shorting across R4 and removing R2
V1 is a pulse signal used to drive the transistor that simulates your 3.3V device output. it's just a signal source used for part of the example.. it's not part of the level shifter. i will post the waveforms from the circuit in operation if you like, then you can see what's going on in it.
Mikebits said:As I tried to elude to, your 3.3v logic device will drive TTL compatible parts. All you need is a cmos inverter with TTL compatible inputs.