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# GPG

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## Posts posted by GPG

1. ### Stupid op-amp question

I thought that 0.05V drop in the original diff-amp was negligible, but it's not when it is amplified with a gain of 22.
~43.5mV, 23 gain
The LM34 has an NPN emitter-follower with resistors-to-ground output.
Its increase in quiescent current of only 15uA at 75 degrees F occurs only in its emitter resistors, which will have 0.75V across them, and therefore calculate to total 50K ohms
Therefore it is not capable of sinking any current from a load that has a positive voltage source like our diff amp that sources 25uA.
Capable of doing so down to 5
2. ### Stupid op-amp question

Previous post

gain of 22.
Gain of 23
The sensor is easily able to drive a 10K load. The amp is probably stuffed through shorting the outputs.
3. ### Stupid op-amp question

In his original circuit, the output will be 6.6V It only goes to 7.6 volts in your modified design. There is nothing wrong with the original design that requires modification, and it provides much better common mde rejection since the gain from both inputs is equal.

4. ### Designing a computer based voltmeter

a site with a similar project.
.

http://www.dutchforce.com/~eforum/index.php?showtopic=1556
5. ### Mysterious Resistor?

The NE5532 is damaged. Replace it.

6. ### Stupid op-amp question

if my math is correct, I should have a gain of 22. For my example of V1=0.7V and V2 = 1V, the output should measure 6.6V,
Correct
7. ### Designing a computer based voltmeter

Bits of resolution for voltage measurement

8. ### atx power supply for robot

http://www.uco.es/dptos/electro/electronica/documentos/ele2N3055-D.pdf
If forced beta = 10 you have a good margin.

9. ### KVM switch circuit / Multi-pole double throw switch

Look at
http://www.ee.washington.edu/stores/DataSheets/cd4000/74c244.pdf

10. ### KVM switch circuit / Multi-pole double throw switch

How are you getting bidirectional from this snippet of schematic? I do not see that. I see input and output clearly stated. Author states he is trying to light LEDs with the switch.

MP

The 4053 is an analog bidirectional switch.
Looking at the pinning of the 157 it is easy to make the assumption that it is too. The OP saying that he was trying to switch between 2 leds lead me to the possibility that he had made the same.
11. ### Temperature sensitive fan speed controller

http://www.micrel.com/product-info/products/mic502.shtml

12. ### DTMF

http://www.electronicsforu.com/EFYLinux/circuit/jun2003/CI-2-DTMF.pdf

13. ### Designing a computer based voltmeter

What resolution do you need?

14. ### temp sensor cooling system

Presuming you are monitoring the cylinder head temp, you will need a thermocouple or RTD for these temperatures.
Sparkplug mtg one here
http://www.performancetrends.com/DatamiteTemperaturePictures.htm

15. ### KVM switch circuit / Multi-pole double throw switch

The 157 is not a bidirectional switch

16. ### scr firing circuit for ac motor speed control

The 5V polarity. Resistor in series with base of pulse transitor. Diode across be of same

17. ### Which one do i use?

The suffixes are package types. N is the plastic DIP type. Go to the manufacturers site for others.

Try this

19. ### Need Datasheet D17072 from NEC

www.necel.com/cgi-bin/nesdis/dl_ docpdf.cgi?lang=E&litcode=U11450EJ1V0DS00
www.necel.com/micro/ods/eng/list/17K/UPD17072.html
2 minutes

21. ### Variable Freq Drive

This might help:
www.intersil.com/data/an/an9642.pdf

22. ### Not your average charger!

It is a load of rubbish. While static charges of several KV can be picked up on an antenna, the current is so small that charging a deep cycle battery from such an arrangement is not possible.

23. ### help, help, help, it's too hot

Another
http://www.linear.com/prod/datasheet.html?datasheet=163
Google "cold junction compensation". You cannot expect accurate results from a thermocouple without taking this into account.

24. ### help, help, help, it's too hot

www.national.com/ms/LB/LB-24.pdf

25. ### need help with pioneer cd player

The transformer probably has an internal fuse. Some transformers have the connection between the primary winding and the fuse on a unused pin, others require peeling off the outer layer of insulation to locate.

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