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| Difficult breadboading a LM324N |
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| Kleinstein:
The LM324 should go to a defined state with floating inputs, as it does not have bias current compensation. So with open inputs they just miss the base current for the input stage. So most of the time it's OK to leave the inputs open. The better way is to connect the inv. input to the output, making it a follower. The LM324 pinout is not even that difficult, it's rather symmetric and easy to remember. For decoupling on the breadboard, I some times / for a few parts I have have there have the decoupling cap directly soldered on top of the chip. For the LM324 / LM358 or similar even an electrolytic cap (e.g. 10 µF) is "fast" enough and even shows the polarity. The problem with a 4 fold OP is more that everything is so close together. So I prefer dual OPs. The cross over distortion of the LM324 / 358 sometimes gives some unpleasant effects. |
| tggzzz:
--- Quote from: Kleinstein on August 12, 2019, 07:47:09 am ---For decoupling on the breadboard, I some times / for a few parts I have have there have the decoupling cap directly soldered on top of the chip. --- End quote --- Agreed, but most people using a solderless breadboard wouldn't know that was beneficial. Plus if you are doing that, why not go straight to "decent" manhattan/deadbug/ratsnest techniques? |
| magic:
--- Quote from: Kleinstein on August 12, 2019, 07:47:09 am ---The LM324 should go to a defined state with floating inputs, as it does not have bias current compensation. So with open inputs they just miss the base current for the input stage. --- End quote --- Input bias isn't cancelled but the base current of the second stage may be cancelled by deliberate imbalance of transistors Q19, Q2, Q5 such that a constant current is injected into Q6, roughly sufficient to sink its collector load. Then, when the loop is closed, the input stage would only supply a minor correction to get it perfectly right. I'm not saying that they bothered, though. |
| Brutte:
The problems of solderless breadboarding only come from the low quality breadboards and jumpers. If you buy a decent ones with phosphor-bronze nickel plated contacts that have indent to hold the leads in the center, unless you mechanically violate those, work just fine. But if you spill a coffee (with sugar), push in a >-1mm2 wire or TO220, use dirty components or try to bend breadboards, etc, well then even a phsphor bronze won't help and you'd better use soldered breadboard. I'd also recommend using tinned jumper wires. The LM324N is absolutely fine as long as you use 2 - 3 boards stacked. With single board it is indeed PITA. The breadboards that I use look like this one from Distrelec (except mine were half the price). The power line bus can be detached and the cores can be stacked so with 2 boards you will get 63 rows that have 5-2-5-2-5-2-5 tie points (5 holes - 2 voids - 5 holes - ...... ) and if you stick LM324 in the center, there is a plenty of room for connections. |
| dcbrown73:
--- Quote from: tggzzz on August 12, 2019, 07:51:28 am ---Agreed, but most people using a solderless breadboard wouldn't know that was beneficial. Plus if you are doing that, why not go straight to "decent" manhattan/deadbug/ratsnest techniques? --- End quote --- The only issue I have with manhattan / deadbug / ratsnest is I'm learning and am likely to need to move and change things often as I learn. If I'm actually soldering and desoldering to change everything. That can take 15-30 minutes of learning and turn it into hours. Not to mention, I'm probably sure to mangle a few components in the process. Maybe I breadboard it and once it's functioning to some extent. Move to a different method for further testing? |
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