Quote: Does anyone remember "veroboard"? I believe it was British-made, the original board with a matrix of holes and parallel copper tracks along its full length. From my experience, boards with pre-defined copper tracks are pretty common. I can find it at RatShack, local electronics...

If not biased properly, impedance measurements will give misleading results. Most likely, the DMM uses a constant voltage method and measures the current flow. Since the amplifier is an active device this will give incorrect results since the amplifier is driving the ouput as well. In other...

Capacitors can smooth out transients but in terms of switchers, inductor-less (capacitor) voltage converters typically have poor load regulation. Load variations over several mA can seriously affect the voltage. The way I see it, all switchers are a headache unless absolutely necessary (weight...

Quote: the analog devices chip seems to absorb some RFI from my cordless phone All op-amps may be subject to a phenomenon called envelope detection. Similar to a cheap AM receiver, the out of band RF signal is demodulated by the nonlinear base-emitter (gate-source) junction at the...

Unless offset trimming is absolutely necessary the op-amp operates normally with the offset terminals unconnected. This would involve either cutting off the pins or bending the pins so they don't go into the socket. You might want to contact Monolithic to ask if there's any trim circuitry for...

Tips are to be cleaned before soldering but not after soldering. I believe this prevents the tip from oxidizing when it is not in use.

Quote: With FET-input op-amps, you have to work pretty hard to get more than about 20mV of DC offset, which is completely ignorable in most circumstances, given that the signal level is hundreds of millivolts at minimum. It's with bipolars, where offsets can be multiple volts, that you have...

Yes, it's true for the higher grades, the limits for some specifications are actually guaranteed. In the case of the OPA627, each chip in the higher grade is tested/rejected for noise while the lower grade is only sampled for noise. Nonetheless, for some important specifications like open...

1200 mAh for a 9V? That strikes me as farfetched when a 1.5V C or D cell has same number of current-hours. If the spec is true, then the 9V has 6 times more power than the C or D cell. I really don't think so.

The different grades of op-amps aren't sorted by anything that human ears can discern. The different grades of OPA627 are sorted by minor variations in: offset voltage (you can't hear DC) bias current (you still can't hear DC) noise (.8uVp-p vs .6uVp-p) common mode rejection (110dB vs 116dB)...

I don't think SO or (T)SSOP packages should be ruled out. Practically nothing comes out in through hole nowadays. There are many reasons for this but smaller surface mount packages have less inductance and more ground capacitance, a must for high performance mixed-signal chips. I've soldered...

Noise isn't calculated that way. The graphs given are spectral noise densities. As the name might imply the noise at a specific frequency is 0 just as the mass of something is 0 if the dimensions are infinitesmally small. Therefore, the noise is calculated as an integration over frequency...

Quote: And actually I think it is great that people have contrary views - nothing better than a healthy debate. And well done to PPR for being prepared to stand up and justify his views. I respect the views of both ppl and PPR - that makes it interesting when they differ. You might...

The circuit doesn't strike me as particularly good. First of all, the op-amp is used in inverting configuration. Not the best choice since non-inverting configuration would be able to isolate potentiometer impedance. All the impedances are extremely close, 5.1k-15k, which can lead to interaction...

Um. Mind you, the OP281 uses 4uA/channel. The ad8610 uses 3,000 uA/channel. It's all about a different set of priorities. So let's say you're stuck in space with several AA batteries, the OP281 would last about oh... say 1000 times longer. Noise at a specific frequency is meaningless. The...

The factoid about the CHA47 is not entirely correct. Slew rate is not doubled because slewing is mainly an input stage issue. Doubling the op-amps will definitely halve the required output drive but will not change the slew rate.

Actually, oscilloscopes aren't typically used for noise measurement. They are useful for qualitative observations. The typical tool used is a true-RMS meter or a FFT spectrum analyzer (for low frequencies). A good figure of merit can probably be obtained with a good true-RMS multimeter. A...

Why would one use 2% silver for surface mount? It has a higher melting point and is more difficult to re-work. Not exactly a plus in my book. I'd recommend Kester 44 core rosin, 63% tin, 37% lead, 1mm diameter. I'd also get some isopropyl alchohol to clean the flux off after.

Many people appear to have oscillation problems. Using low gain designs definitely does not help. The stock CMOY has moderate gain so it's usually not as big an issue. Maybe a feedback capacitance or output resistor should be included in the schematics of the current doubled designs.

It was probably cheaper to not include switchers in the Headroom low-end products. The mid-level amps (portable) still appear to have DC-DC converters. I feel switchers have a bad reputation due to their misuse. They are more difficult to use so I suppose it isn't surprising.

There are MANY different schematics for amps. The original basic CMOY would use one 2134 for the entire amp. The current-doubled amp which has various names, usually CHA47, uses one 2134 per channel. I've looked at several audio waveforms on a scope. They usually look alright. However, since...

While a DC-DC converter (switcher) would allow the use of less batteries, batteries would run out sooner since the same power would have to be extracted from less batteries. I believe the folks at Headroom use Datel DC-DC converters in their portable products so it's not an impossibility. The...

I hope you don't take any offense at these questions: 1. How much experience do you have with a 'scope? 1. Have you tested the 'scope with a simple function generator such as a sine/square wave generator?

The LM6171 contains a single op-amp in a package while the LM6172 contains two op-amps in a package. While some purists would recommend using two LM6171, a single LM6172 is cheaper and more compact. Just take a look at the datasheets: LM is www.national.com OPA is www.ti.com AD is...

While it's true that a box will have zero electric field inside, flat planes also shunt electric fields. For example, if one uses a unbroken copper plane for circuits, the RF interference near the plane is greatly reduced.