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345 results found, displaying items 281 - 300
Tiny microcontroller provides 4-channel A/D conversion for a PC serial port
Microchip’s PIC12C671 is a lowcost 8-pin microcontroller that has everything needed to perform a four-channel 8-bit analog-todigital conversion without external components. To create a plug-in four-channel analog-to-digital converter for a PC, the...
Improved efficiency fan-speed control
Reducing the operating speed of a system cooling fan not only saves power, but also extends the operating life of the fan and lowers acoustic noise. Fan speed can be controlled by sensing the ambient temperature in the system enclosure and reducing...
Edit and generate your own analog stimulus waveforms
In cases where low frequencies are acceptable, a user-defined analog waveform can be generated using the design presented. The circuit employs a low-power 12-bit digital-toanalog converter (DAC) connected to the parallel printer port of a personal...
Power amplifier buffer features digital bias adjustment
The day may be near when every amplifier application can be served simply by finding the right off-the-shelf standalone chip. Maybe. But for now, many jobs require that even the best monolithic devices be supplemented with a sprinkling of active...
Single-transistor constant-current generator
Perhaps this circuit is stating the obvious, but sometimes the obvious can elude us! Though not as good as many other constant current generators, it’s very simple and very inexpensive. The figure shows the...
Effective AGC Amplifier Can Be Built At A Nominal Cost
Using the circuit presented here, you can construct a very inexpensive AGC amplifier with the following features: a dynamic range greater than 50 dB; negligible distortion to the output waveform; fast attack and slow decay; an adjustable output level...
Hybrid Digital-Analog Proportional-Integral Temperature Controller
A classic scheme for precision temperature control is the proportional-integral or “P/I” algorithm. In this method, the heater control equation consists of two terms. One term (“P”) is proportional to the instantaneous error differential between...
An I2C Fan For PCs
The ultimate solution to elegant fan control and monitoring in the PC would be a cooling fan with an I2C or SMBus interface built in. However, this doesn’t exist, at least not yet. A close emulation of this type of functionality can be...
Electronic Flicker Pulsing Suppresses EMI Problems
Pulsing circuits generate EMI that can affect sensitive circuitry and adversely contribute to the spectral signature of the equipment. “Flicker-noise” concepts, derived from chaos theory, have been employed to efficiently pulse circuitry while...
Vocal-Aural Feedback Digital Delay Device
When humans speak, many complicated, interrelated, and not completely understood neural and muscular processes must all coordinate. Most of these processes aren’t accessible to simple investigation, but one important speech-production mechanism is...
Novel Decoding/Threshold-Sensing Technique
Here’s an Idea For Design that’s more Idea than it is Design. Using inexpensive memory devices, you can construct a voltage, current, or count sensing system that can be permanently programmed for one set of input conditions or...
Nanopower VFC Includes Self-Compensating Charge Pump
Of the many starting points for voltage-to-frequency converter (VFC) designs, one of the golden oldies is the classic diode-capacitor charge pump. An example of this fundamental circuit is represented by D1, D2, C1, and C2 (...
Simple Soft-Start Circuitry Provides Long Startup Times
Many dc-dc converters require relatively large amounts of input current at startup (when input power is first applied). A soft-start function minimizes this large input current by gradually increasing the switch-current limit at startup, slowing the...
Simple Addition To Logarithmic Compressor Reduces Noise
Using the SA571/NE571 as a compressor can create a problem in some applications. Unlike most conventional compressors, which only compress above a threshold level, the SA571 compresses a 100-dB dynamic range to 50 dB. When viewed on a log-log plot,...
Temperature-Compensated LCD Bias Supply Uses A Single Control IC
Many applications require a simple method for getting multiple outputs from the power supply. One way to achieve this goal is by using charge pumps. The schematic shown in Figure 1 is an LCD bias...
Wide-Range Programmable Negative Regulator Conserves Power
The circuit described here supplies 0 V to −40 V for those applications that require a variable programmable power supply, such as in automated testing systems, battery-discharge-curve simulation, and when driving heating elements to various...
An almost-accurate rotation center
Most motion-control applications typically employ an optical disk or Hall-effect device in order to accurately count the number of times that a motor shaft rotates. While the following circuit lacks the accuracy of both the optical disk and...
ADC clock gating circuit maximizes data throughput
When reading the data from a serial analog-to-digital converter (ADC), it may be desirable to use a serial port available on a microprocessor or a digital signal processor. If the ADC offers high resolution (i.e., 16 bits or greater), it may actually...
Optically isolated precision bipolar current source
One of the most frequently requested instruments in the field of in-vivo and in-vitro neurophysiology research is the galvanically isolated neural stimulator. Applications in this field require an accurate, voltage-programmable, bipolar current source...
Current-sensing LDO voltage regulator
When designing battery-operated devices, battery contact chatter can be prove to be a difficult problem to overcome. When the chatter occurs at a critical time, the results can often be devastating. For instance, if a memory write takes place during a...
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