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Hello, We've built a NiMH-charger with the MAX712 according to the circuit at page 1. http://pdfserv.maxim-ic.com/en/an/AN936.pdf The only difference is, that R4=0R2, R9=6R8 and a Schottky between Q1 and Battery. (before we used NiCd with Max713 and because of that we added the discharge...

Hello again, I've almost solved my problem :-) The 987mV is exactly the calculated result for the x10/x100 probe with 1MOhm input resistance. To get 1000mV the 969k should be 976k or the 4,494M a little bit lower. I don't know the real values, does anyone? My biggest problem is: Can I change the...

Hello, I'm having problems with my self-built measuring device. The input stage looks like this: 1V ------3M6-----------n.inv. amplifier x1,6------- 1V | | 1,125M 5M4 | | GND GND When I connect a x1/x10 probe I get with 1V/10V...

Hello, I've read that p-channel IGBTs can be made but have never seen one.Is there a reason why only n-channel types are around?

@Noway2 look at my post from 31 July 08 for some details.I switch 2 channels 1Vpeak dc to 10 MHz to an opamp with switchable gain.Perhaps a series connection of n-channel and p-channel Mosfets works.I don't know.Sounds complicated anyway.Also capacitance is an issue. My problem is that the...

Hi all, naturally you're right.It is a desperate attempt to boost the specs of the device at unacceptable costs.I must find another way to cure the problem or resign to the actual state of accuracy. Thanks

I agree with davidbeach.The magnetizing current is developed by the net-voltage over the magnetizing inductance.In an idle transformer there is little voltage drop over Lp1 or R1 because the magnetizing current is relatively small.When a load is connected to the secondary winding the secondary...

Hi NG, relating to my previous question (31 Jul 08) I've found out that the specifications vary pretty much from part to part. I'd like to test the SOT23-JFET before soldering it to my board. Has anyone heard of or built a test fixture for SOT23? Any ideas?

@8060A: You're right, I pinch off the 309 with -9,5V through a Mosfet and switch them on via a 180k S-G-Resistor.Because also frequency is involved I added 39k in series to the Mosfet. Your idea to increase the feedback resistor is probably the best way.Currently I use 300/200 Ohm as...

Hello NG, I use two JFET MMBFJ309LT1G to switch 2 different channels to an inverting amplifier (OPA656U) with a gain of 0,6 (JFET3 closed). Furthermore the gain can be switched to 6 by opening this third JFET increasing the feedback resistor respectively. All this worked in my previous layout...

@ waross, I've tried to find a URL for our used switch but couldn't find one. I'm completely fed up with corporations that aren't able to find their own parts like Philips....and it seems also ITT Cannon. But perhaps they don't manufacture it anymore. I'll try to upload our old pdf. Our future...

Thank you all for your comments. They've helped me a lot. Reed relays are inappropriate, I think, because the device will be used in a power electronics environment. For Mercury-wetted relays I'll check the www, haven't heard of them before. But in one respect I agree with many of you: I'll buy...

@ all thank you for all your contributions. Probably I must face the truth that it is difficult to replace an ordinary push switch assembly like the ITT Cannon TJ type we've used so far. The problem is that hardly any distributor in Germany has such assemblies available. I was looking only for...

@ operahouse & itsmoked, that's a very valuable information. I've checked my TQ-Relay and it has Gold-clad silver contacts. Now it gets complicated, I fear.http://delta.octopart.com/Panasonic__TQ2-L-5V.pdf

@ waross no, it's a usual TQ-relay by Panasonic (5V). When using solid state relays I suspect leakage currents and capacitances spoiling my signal. I'm just reading something about thermal emf of relay contacts, but shouldn't the same apply to switch contacts? There must be a significant...

@ all I'm certainly aware of the relay specs but can anyone tell me the difference between a relay contact and a switch contact? That's the question that puzzles me.

Hi Forum, I was going to replace the push button switch in my input voltage divider by a bistable relay. Now I discovered that the relay has a minimum permissible load (10µA @ 10mVDC). Can I replace the switch by the relay and ignore the minimum load? Why doesn't the switch have such restraint...

Hello Forum Just as I hit the send button I had the right idea that the temp drift could arise from the external protection diodes. BTW I hadn't mentioned it, sorry.

Hello all, I use the AD8033 as a G=1 buffer for my voltage divider. When I short the +input to gnd I get +0,4mV at the output. If I now heat up the circuit I get +0,1mV. Now I connect 100k to gnd and get 1,3 mV at the output-would have expected less according to Ibmax=40pA. If I now heat up the...

@VE1BLL It's a Hameg 1:1 / 10:1 probe and it has this resistance in the 1:1 range. Check your probe if you don't believe it. @BrianG The divider is a 1:0.9 which means the 100k is up and the 900k at ground. The input capacitance of the amp/stray I estimated at 16p because I needed 150p across...