The circuit works with two 741 opamps and provides better than 20 dB gain in each channel. A better type op-amp will give a better noise figure and bandwidth. ..
Opamps are very useful. But one of their major drawbacks is the requirement of a dual supply. This seriously limits their applications in fields where a dual supply is not affordable or not practicable. This circuit solves the problem to a certain extent. It provides a negative voltage from a single positive supply. This negative voltage together with the positive supply can be used to power the opamps and other circuits requiring a dual supply. The circuits operation.....
built this version pocket amp, which has a 10K ohm volume control and an acoustic simulator front-end by Chester Simpson (see design by Fred Peng below). He used OPA134 opamps and set the gain to unity because his CD player`s line out supplies more than adequate drive voltage. Full details can be found at DIY Zone (in chinese only). His system consists of a Rega Planet CD Player and Audio Technica ATH-f15 headphones...
The phono preamp shown has an accurate RIAA equalisation curve, is very quiet, and offers far better sonic performance than the vast majority of those seen in magazines and application notes. Like most other ESP projects, it is very tolerant of opamps but the NE5532 dual op-amp is a good choice. This is a low noise, high speed device with excellent characteristics, and is inexpensive. It is ideally suited to this sort of application. Noise is extremely low, since any.....
The unit is simple to build, and does not need really low noise opamps, since they only act as a modulator oscillator. I used 1458 dual types in the prototype, and they are more than good enough. The transistors can be any low noise NPN type, and they are simply buffers, ensuring a high input impedance and low output impedance. If the unit is to built into an amplifier, it may well be possible to leave out the input transistor, since a low impedance drive circuit is.....
Fred Forssell`s circuit (figure 3) has the differential input stage of a true opamp with a high common-mode rejection ratio (CMRR) and a mu follower output stage (biased at 12mA). The open loop gain is about 510 (30 from the first stage, 17 from the second). When configured for a closed loop gain of 18, the performance approaches that of solid state opamps: THD < 0.1%, Rout = 8 ohms, Fh > 400 kHz and s/n ratio = -86dB. Despite the low output impedance, the load.....
Building a headphone amplifier is like building a power amp - only the current demand is just a little bit lower (about a factor 100). Various designs can be found in the internet, and it is relatively easy to integrate the proposed crossfeed filter. I designed my own (see the picture) which is op-amp based. I know, many hi-fi enthusiasts say "yuck" to opamps, but note that even in many so-called "High-End" CD-players, opamps are found in the signal path for amplification.....
This article discusses several opamp-based headphone amplifier circuits, including suggestions for selecting opamps, input coupling and filtering, high current output stages and power supply options. There are no recommendations for specific opamp brands or models. For tube devotees, there is also an introduction to designing with tube amp-blocks. Tube amp-blocks (AC feedback amplifiers and tube opamps) are not as compact as their silicon brethren, nor do they measure as.....
The primary advantage of this method of bridging is that no additional components are needed (which means that it is cheap), and there is no signal degradation from additional opamps in the circuit path. The results are at least as good as using an external circuit, but you have to be prepared to modify your amplifier. This is not a good idea if it is under warranty! There is a negative though. Most amplifiers have a small and usually almost inaudible thump at turn-on and.....
the AD844 was still used, but this time the feedback loop went all the way from output and back to input. The DC servo was removed and the current source was made faster, using an extra transistor. The local feedback was turned into global feedback, lowering the distortion and output impedance, but that also introduced some other problems. I like high bandwidth and slew rate, because it gives a high security margin before phase errors appear in the high frequencies. Also I.....
The figures below illustrate using opamps as active 2nd order filters. Three 2nd order filters are shown, low pass, high pass, and bandpass. Each of these filters will attenuate frequencies outside their passband at a rate of 12dB per octave or 1/4 the voltage amplitude for each octave of frequency increase or decrease outside the passband. ..
When an antenna is attached, (or even if not, in the presence of a strong RF field) the field strength meter has a moving coil meter to indicate relative field strength. The box holds a Schottky diode detector, a DC amplifier, and a meter display. If the parts used in construction are the same values shown in the schematic, the meter shows full scale ("+3db" on the surplus store VU meter movement) when the output of the Schottky diode detector is between 1.6 millivolts.....
Another method of using opamps to regulate a power supply is shown below. The power transformer requires an additional winding to supply the op-amps with a bipolar voltage (+/- 8 volts), and the negative voltage is also used to generate a reference voltage below ground so that the output voltage can be adjusted all the way down to 0. Current limiting is accomplished by sensing the voltage drop across a small resistor placed in series with the negative supply line. As the.....
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