Rongge

You can use three discrete transistors to build an operational amplifier with an open-loop gain greater than 1 million (Figure 1). You bias the output at approximately one-half the supply voltage using the combined voltage drops across zener diode D 1 , the emitter-base voltage of input transistor Q 1 , and the 1V drop across 1-MΩ feed-back resistor R 2 . Figure 1 . This ac-coupled inverting op amp has an open-loop gain of 1 million. R 1 and R 2 set a closed-loop gain of −10. Resistor R 3 and capacitor C 1 form a compensation network that prevents the circuit from oscillating. The values in the figure still provide a good square-wave response. The ratio of R 2 to R 1 determines the inverting gain, which is −10 in this example. You can configure this op amp as an active filter or as an oscillator. It drives a load of 1 kΩ. The square-wave response is good at 10 kHz, and the output reduces by 3 dB at 50 kHz. Set the 50-Hz low-frequency response with the values of the input ...

The Uninterrupted Power Supply in an IC . Cymbet Corporation announced the availability of the EnerChip™ CC CBC3105 smart solid state battery. The CBC3105 combines the award winning EnerChip battery with integrated input power conversion, battery management and regulated output capabilities. The Cymbet EnerChip™ CC is a smart rechargeable solid state battery Uninterrupted Power Supply (UPS in a Chip™) that provides power backup to microelectronic devices when main power fails. The EnerChip CC provides power supply monitoring and switches over to the internal solid state backup battery when the supply drops below a set threshold. The EnerChip CC product family can provide anywhere from several hours to several weeks of backup time.  Simple Uninterrupted Power Supply in an IC Circuit Diagram   The CBC3105 is an ideal solution for design engineers who need a compact device to back-up a Real Time Clock or Microcontroller during power failure where coin cell batteries or super ...

Most engineers will recognise the problem: Your circuit needs a stable 1 or 2 MHz clock generator (in the author’s case it was for a Pong game using an old AY3-8500). A suitable crystal is not to hand so you cobble together an RC oscillator (there are plenty of circuits for such a design). Now it turns out that you don’t have exactly the right capacitor so a preset pot is add e d to allow some adjustment . Before you know it the clock circuit is taking up more space on the board than you had hoped.  Providing the application does not demand a precise clock source a tiny 8-pin microcontroller may offer a better solution to the problem. It needs no additional external components and an old ATtiny15 can be found quite cheaply. Another advantage of the solution is that clock frequency adjustment does not involve changing external components and is not subject to component tolerances.  The microcontroller’s internal RC oscillator is already accurately calibrated to 1.6 MHz. With i...

Around us will be a large amount of energy scattered in space, are the RF waves emitted by TV channels, radios, cell phones, computers, etc.. What most people do not know is that we can capture the scattered energy and transform into electricity.  To capture any wave, we have to have a coil in the same resonant frequency, we can also simply capture radio signals by a common antenna and light an LED if we get a strong signal.Setup is simple. You will need an antenna too high, most likely on roof or on top of a mast and make sure that isolated and fixed. Then connect the enameled copper wire antenna and take it to the circuit. Power of the environment by using an antenna Circuit