Single ended signal over TL072 to a differential line

You dont say how large the signal is, or the bandwidth, or cable type

Assuming twisted pair cable, and say 20K B/W you could start by having a pseudo differential signal. Connect the output of your 072 to one of the lines via a 50 ohm resistor, connect the other cable to ground with another 50 ohm resistor, this will look like a balanced signal to a differential receiver and have good common mode rejection, maybe about 6dB worse than a fully balanced output

martin

Ai - sorry! input signal is "a few" millivolt ( usually - I will need to have potis to fine-tune the amplification I think ) but can go up to as much as 5 Volts in the seldom extreme. The lines are an ethernet Category 5 cable, 8 meters, running straight into a ( not defined ) differential input of a PCI-datasampling-card in a PC. The sensor is a small K-Band transceiver ( aka radar ;) from InnoSent ). I do not know where to add the resistors to shape and tune the output of the combined opamps. I'm lost if and where to add the poti's to control the amplification and so on. I hope that there might be a website with an example circuit which I could adapt to my needs.

will show you the basics

martin

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If he uses a TL072 dual opamp (good choice you made), he might as well use the 2nd-half to make a full-differential output.

Yeah, I know, but he did say single ended, I had thought of mentioning diff drivers etc. But there is too much "Nah you dont want to do it that way" around here, when a 072 will do the job.

Anyway, lets see how the OP gets on.

martin

Okay, Thank you for that first example. My boss gave me this one here:

Digital Media is not really that kind of study teaching one how to design line drivers I am afraid... Maybe you can interpret the missing bits or the concept he uses there.

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You'll need feedback components for the two driver ICs, and don't forget the cable-matching resistors Martin pointed out. The receiver end needs input-protection stuff, and a real diif amp, see Martin's part selection - you likely don't want a power opamp for a receiver!

have a look at TI's DRV134 data sheet.

martin

a bit more here

martin

The single opamp on the right I added just to get the concept clear - the PCI-Card has variable impedance differential inputs, the software can set a whole range of details like input capacitance, input impedance and so on. I just have my headaches with the part on the K-Band transceiver's side, how to get the input-levels configured correctly - I never before worked with differential line drivers other then resoldering ethernet-sockets.

On Wed, 18 Apr 2007 12:42:52 +0200, in sci.electronics.design Rüdiger Leibrandt wrote: I never before worked with

Cut off the connectors and use a terminal strip. It has the added advantage that nobody will steal the cable for expanding the network

martin

Okay - the last word after a lot of datasheet reading is now a MAX435 - it's a wideband Transconductance Amplifier. I just need to find out how to give it a variable gain without ruining the impedance of it's output, and then I am fine.

Thank you all very much for the help you provided to me!

it's

Well a postscript then ;) Looks like the Maxim thing is obsolete. You'd have been better off with an AD8132.

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We have 30 of those Maxim IC's laying idly around - someday we would have thrown them away otherwise.... Thats active trash-reduction ;)

Having read this thread so far, it sounds like going for 4 to 20 mA SCADA transmitter is the way to go.

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