Showing posts with label high. Show all posts
Showing posts with label high. Show all posts
Monday, September 2, 2013
Audio Amplifier with High Clarity Circuit
Circuit Diagram
Description
Description
The heart of the circuit is TDA7294 which acts as an amplifier the right and left input feded from the pre amplifier circuit is amplified after passing through the noise filter which contains an RC circuit, the volume is controlled by the variable resistor 47k. and the automatic gain control is provided by the operational amplifier circuit opp amp IC249 For both right channel and left channel., the speaker used is an 8 ohms 40 watts speaker.
Tuesday, April 9, 2013
Mini High Voltage Generator Circuit
Here’s a project that could be useful this summer on the beach, to stop anyone touching your things left on your beach towel while you’ve gone swimming; you might equally well use it at the office or workshop when you go back to work. In a very small space, and powered by simple primary cells or rechargeable batteries, the proposed circuit generates a low-energy, high voltage of the order of around 200 to 400 V, harmless to humans, of course, but still able to give a quite nasty ‘poke’ to anyone who touches it.
Quite apart from this practical aspect, this project will also prove instructional for younger hobbyists, enabling them to discover a circuit that all the ‘oldies’ who’ve worked in radio, and having enjoyed valve technology in particular, are bound to be familiar with. As the circuit diagram shows, the project is extremely simple, as it contains only a single active element, and then it’s only a fairly ordinary transistor. As shown here, it operates as a low-frequency oscillator, making it possible to convert the battery’s DC voltage into an AC voltage that can be stepped up via the transformer.
Using a centre-tapped transformer as here makes it possible to build a ‘Hartley’ oscillator around transistor T1, which as we have indicated above was used a great deal in radio in that distant era when valves reigned supreme and these was no sign of silicon taking over and turning most electronics into ‘solid state’. The ‘Hartley’ is one of a number of L-C oscillator designs that made it to eternal fame and was named after its invertor, Ralph V.L Hartley (1888-1970). For such an oscillator to work and produce a proper sinewave output, the position of the intermediate tap on the winding used had to be carefully chosen to ensure the proper step-down (voltage reduction) ratio.
Here the step-down is obtained inductively. Here, optimum inductive tapping is not possible since we are using a standard, off-the-shelf transformer. However we’re in luck — as its position in the centre of the winding creates too much feedback, it ensures that the oscillator will always start reliably. However, the excess feedback means that it doesn’t generate sinewaves; indeed, far from it. But that’s not important for this sort of application, and the transformer copes very well with it.
The output voltage may be used directly, via the two current-limiting resistors R2 an R3, which must not under any circum-stances be omitted or modified, as they are what make the circuit safe. You will then get around 200 V peak-to-peak, which is already quite unpleasant to touch. But you can also use a voltage doubler, shown at the bottom right of the figure, which will then produce around 300 V, even more unpleasant to touch. Here too of course, the resistors, now know as R4 and R5, must always be present. The circuit only consumes around a few tens of mA, regardless of whether it is ‘warding off’ someone or not! If you have to use it for long periods, we would however recommend powering it from AAA size Ni-MH batteries in groups of ten in a suitable holder, in order not to ruin you buying dry batteries.
Circuit diagram:
Warning!
If you build the version without the voltage doubler and measure the output voltage with your multimeter, you’ll see a lower value than stated. This is due to the fact that the waveform is a long way from being a sinewave, and multimeters have trouble interpreting its RMS (root-mean-square) value. However, if you have access to an oscilloscope capable of handling a few hundred volts on its input, you’ll be able to see the true values as stated. If you’re still not convinced, all you need do is touch the output terminals...
If you build the version without the voltage doubler and measure the output voltage with your multimeter, you’ll see a lower value than stated. This is due to the fact that the waveform is a long way from being a sinewave, and multimeters have trouble interpreting its RMS (root-mean-square) value. However, if you have access to an oscilloscope capable of handling a few hundred volts on its input, you’ll be able to see the true values as stated. If you’re still not convinced, all you need do is touch the output terminals...
To use this project to protect the handle of your beach bag or your attachecase, for example, all you need do is fix to this two small metallic areas, quite close together, each connected to one output terminal of the circuit. Arrange them in such a way that unwanted hands are bound to touch both of them together; the result is guaranteed! Just take care to avoid getting caught in your own trap when you take your bag to turn the circuit off!
Source by : Streampowers
High CMR Isolation Amplifier Circuit
transients that are generated by the switching of the inverter transistors. Here’s the figure of the design circuit;
Developed as a compact low-cost solution for just this type of design problem, the HCPL-7800 High CMR Isolation Amplifier allows designers to sense current in extremely noisy environments while maintaining excellent gain and off set accuracy. It exhibits outstanding stability over both time and temperature, as well as unequaled common-mode transient noise rejection (CMR). To achieve such a high level of performance, the HCPL) analog-to-digital converter (-7800 combines several different technologies, including a state-of-the-art sigma-delta (ADCm standard-cell), chopper-stabilized internal amplifiers, a fully differential circuit topology fabricated on a 1 CMOS process, an edge-triggered level-sensitive data encoder/decoder circuit, a high-efficiency, high-speed AlGaAs LED, an advanced photo-detector noise shield, and an efficient “light-pipe” packaging technology. The HCPL-7800 is available in a small 8-pin DIP package, making it the world’s smallest isolation amplifier.
Sunday, April 7, 2013
High Voltage AC Calibrator Circuit Using Op Amp
This a application circuit for calibration. This circuit is called high voltage AC calibrator circuit. In another dimension in sine wave oscillator design is stable control of amplitude. This is the figure of the circuit.
In this circuit, not only is the amplitude stabilized by servo control but voltage gain is included within the servo loop. A transformer is used to provide voltage gain within a tightly controlled servo loop. A voltage gain of 100 is achieved by driving the secondary of the transformer and taking the output from the primary. A current sensitive negative absolute value amplifier composed of two amplifiers of an LF347 quad generates a negative rectified feedback signal. This is compared to the LM329 DC reference at the third LF347 which amplifies the difference at a gain of 100. The 10 μF feedback capacitor is used to set the frequency response of the loop.
The output of this amplifier controls the amplitude of the LM3900 oscillator thereby closing the loop. As shown the circuit oscillates at 1 kHz with under 0.1% distortion for a 100 Vrms (285 Vp-p) output. If the summing resistors from the LM329 are replaced with a potentiometer the loop is stable for output settings ranging from 3 Vrms to 190 Vrms (542 Vp-p!) with no change in frequency. If the DAC1280 D/A converter shown in dashed lines replace the LM329 reference, the AC output voltage can be controlled by the digital code input with 3 digit calibrated accuracy. [Schematic diagram source: National Semiconductor, Inc]
In this circuit, not only is the amplitude stabilized by servo control but voltage gain is included within the servo loop. A transformer is used to provide voltage gain within a tightly controlled servo loop. A voltage gain of 100 is achieved by driving the secondary of the transformer and taking the output from the primary. A current sensitive negative absolute value amplifier composed of two amplifiers of an LF347 quad generates a negative rectified feedback signal. This is compared to the LM329 DC reference at the third LF347 which amplifies the difference at a gain of 100. The 10 μF feedback capacitor is used to set the frequency response of the loop.
The output of this amplifier controls the amplitude of the LM3900 oscillator thereby closing the loop. As shown the circuit oscillates at 1 kHz with under 0.1% distortion for a 100 Vrms (285 Vp-p) output. If the summing resistors from the LM329 are replaced with a potentiometer the loop is stable for output settings ranging from 3 Vrms to 190 Vrms (542 Vp-p!) with no change in frequency. If the DAC1280 D/A converter shown in dashed lines replace the LM329 reference, the AC output voltage can be controlled by the digital code input with 3 digit calibrated accuracy. [Schematic diagram source: National Semiconductor, Inc]
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