# I want to know what do diodes facing opposite each other do?

1. May 7, 2012

### daniel08

Dear Experts.

I like to confirm that operation principle of the attached circuit.

1. what do diodes facing opposite each other do?
2. how to calculate v2 voltage?

Please could you comment on this?
Thanks very much.

File size:
8.1 KB
Views:
720
2. May 7, 2012

### davenn

hi daniel
welcome
interesting, havent seen one using double sets of diodes before
if you ignored the V1 output and the 2 diodes above it then it would be basically a voltage clipping cct ( 1 or 2 diodes down to GND from the logic line and another couple up to VCC)
Bringing the 2 diodes down from VCC to V1 is producing a voltage reference point that will be the sum of the voltage drop across those 2 diodes -- approx 0.7V each

am also looking forward to some other explanations :)

Dave

3. May 8, 2012

### es1

This feels a lot like homework due to the missing information.

Some information we would need to know to answer the question: What's VCC? What's the logic signal? Is the logic level a current signal or a voltage signal? Is the logic signal clamped to VCC or GND by something other than the given diodes?

4. May 8, 2012

### carlgrace

The circuit is a level shifter. v2 is a copy of v1 but the high and low voltage of the logic signal is shifted up two voltage drops. VCC has to be high enough for this to work because the diodes connected between v2 and VCC need to be reverse-biased.