# Unipolar to bopolar pulses

Discussion in 'Homework Help' started by Mavlik, Jul 9, 2013.

1. ### Mavlik Thread Starter New Member

Nov 19, 2012
5
0
Please suggest how to make a bipolar output from the unipolar?
Impulses come from 555 circuit. I have only positive power source (12V DC).

2. ### Ramussons Active Member

May 3, 2013
557
92
Can you give a plot of the required waveform with the voltage levels?

Ramesh

3. ### Shagas Active Member

May 13, 2013
802
74
Reference your output ground to 6v and you've got yourself a bipolar output.

You can get the 6v from the 12v by putting 2 same value resistors for example 1k and 1k and tapping the point inbetween.
Then your output will be taken from the output of the 555 and the ground that you created with your 1k - 1k

4. ### Mavlik Thread Starter New Member

Nov 19, 2012
5
0
Ramussons
Here is a scheme

File size:
22.7 KB
Views:
23
5. ### Ramussons Active Member

May 3, 2013
557
92
Ok, did some experimenting

Your present stream seems to be around 50 Hz and is not a Square Wave (50% duty cycle)

A second 555 is used as a source to generate -11V. An OpAmp is used as a comparator. The input is from your original astable.

You can use a 741 opamp for this application. D1 and D2 can be 1N40xx. D3 and D4 are Zeners. For a 12 V supply, you can go upto 8.2V. You can get Bipolar with 8.7 V amplitude.

Ramesh

File size:
57.1 KB
Views:
18
6. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
657
AC coupling is the simplest solution.

7. ### Ramussons Active Member

May 3, 2013
557
92
Yes, provided the digital stream is 50% duty cycle.

Ramesh

8. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
657
Any duty cycle pulse waveform will be bipolar (± around ground). The ± peak magnitudes will be equal only if the duty cycle is 50%.

Mavlik, what is your application? What does the waveform look like (voltage levels, duty cycle, frequency, etc.)?