Discrete Current Boost/Pulse circuit

Over what voltage range? Is current only forward?

Tim

-- Deep Fryer: A very philosophical monk. Website @

At least this year, they're getting started on their class projects at the _beginning_ of the term, rather than waiting 'til the last minute. ;-)

Cheers! Rich

At what tyre pressure?

Martin

It's not a university electronics engineering project, or any post secondary electronics course related material either. I'm on my own on this one. OK.

-Neil

On Sep 25, 2:58 am, "Tim Williams" wrote: Over what voltage range? Is current only forward?

Tim

Tim, Well that would be between 10 to 12 volts. Current forward only. Yep

-Neil.

Martin, Pressure?..this is a electronics related question, it's a 600 milliamp pulse at 200 milliseconds.

Why do you ask for a "current boost", as opposed to a current source, or mirror, etc. Do you possibly mean a current amplifier, getting say 6mA IN, and delivering 100x more or 600mA OUT.

What do you mean by the phrase, current boost?

Then something like this will suffice. /---o Current sink R1 1k (1.2V) |/ Logic in o---/\\/\\----+-----+---------| | | |\\ R2 | _V_ v 1k > | 2 x | (0.6V) > _V_ 1N914 > R# | | >

| | | +-----+------------+ _|_ GND

R3 = 0.6 / Iout.

Or reverse the transistor and diodes for PNP (change GND to +V).

A transistor like TIP29 should suffice. Actually, a darlington (TIP120, etc.) might not be a bad idea, in which case you will need three 1N914's in series. The transistor will need a small heatsink, as you will be dissipating about 12V * 0.6A = 5W.

Rise and fall time will be under a microsecond. If you need faster, put a

If you need more accuracy, you can use more base voltage (i.e., more diodes in series, or use a reverse-biased zener instead), in which case R3 needs to change accordingly. You can also cascode it:

o Iout | 2.2k (3.3V) |/

Again, flip if you need a source.

Tim

-- Deep Fryer: A very philos> Over what voltage range? Is current only forward?

---

1. When you say "current forward" do you mean that you want the circuit to send current to the load (source current) or do you mean that you want current to come from the load into the circuit (sink current)?

1. How often do you want this current pulse to appear?

2. Is the amount of current to be determined by the load resistance or by the circuit?

-- JF