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  • Users: dau
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  1. dau

    early termination Max712

    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...
  2. dau

    Probe Problem

    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...
  3. dau

    p-channel IGBT

    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?
  4. dau

    JFET Symmetry 2

    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?
  5. dau

    JFET Symmetry

    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...
  6. dau

    relay minimum permissible load

    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...
  7. dau

    offset voltage opamp

    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...
  8. dau

    compensated divider

    Hello Forum, I'm toiling just with a Frequency compensated voltage divider followed by a G=1 buffer. The divider is 100k//150p and 900k//16p,1Vpp up to 10 MHz. Now I adjust it so that the sine-output of the opamp is 0.9*Vin. Channel 1 of a 10:1 probe directly connected to the BNC at the divider...
  9. dau

    Resolver to Digital Conversion

    Hello all, we use an AD2S90 RD-Converter to measure the position of a synchron machine. Everything works fine but: our circuit is integrated in a more complex system which switches off the power supply to our device under a fault condition. At power up the AD2S90 looses its tracking because the...
  10. dau

    AM Radio in Car Part2

    Thank you for all replies. But what is a resistive sparkplug cable? Can I measure whether I have one? Is such an item reasonable? Answering to Higgler: What is an external FM modulator? How do you connect it?
  11. dau

    AM Radio Interference in car

    Hello, I like to listen to AM Radio in my car (Skoda 1998). Every time the motor runs it interferes with an ugly noise in the loudspeaker. An interim seperate supply of the radio lowered the noise level by approx. 50%. So I guess the rest is introduced by antenna pick-up. An LC-low pass filter...
  12. dau

    Driving AC-Motor with Sqare Waves

    I'm going to built an uninterruptible power supply for my 220VAC / 70W heating pump. For simplicity reasons I've chosen a simple 50 Hz sqare wave drive with a usual 12V to 220V Transformer ( H-Bridge). Everything is running as expected but I'm now uncertain whether the motor will resent the...

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