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...
@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...
