hamuro

The voltmeter shown in the schematic diagram below has very high impedance. The range selector uses conventional voltage divider resistors, but since the following pre amplifier uses JFET, the divider can be designed using very high resistance series resistors. This DC voltmeter circuit also featured with low drift. This circuit uses a pair JFETs, which is configured in a balanced-bridge source-follower amplifier circuit. The Q2 and Q1 must be matched within 10% for Idss that will maintains... Read Full Story

When we modulate a carrier signal with amplitude modulation, there will be four frequency components as the result. The first is the modulating signal itself, the second is the frequency carrier, the the latest two are the difference and the sum of the carrier and the modulating signal.  The spectrum of these frequencies can be seen using frequency analyzer.  In radio transmission, the modulating frequency components is completely filtered out since the frequency is far lower than the other... Read Full Story

Using the circuit shown in the schematic diagram below, we can control the low-level audio signals with ±3V variable DC voltage. This attenuator circuit uses a field effect transistor (FET) to shunt the signal to ground. The R2 is used to control the output level (the attenuation level), but you can use other source of voltage signal to control the grid of the FET, such as DAC output, just remember that this voltage is a negative going signal (you can use with DAC which uses symmetric power... Read Full Story

This is a schematic diagram of video amplifier circuit with bi-phase output.  Bi-phase output provides both positive-going and negative-going signal, and can be used as balanced signaling. The main component of this circuit is LM1201.  In this circuit, the inverted video is obtained at pin 10 because of the 75Ω termination to the power supply voltage. The voltage divider on pin 6 is used to set the black level on inverted video (pin 8) to 1.5V. Here is the schematic diagram of the circuit: Read Full Story

This amplifier circuit is very popular audio power amplifier circuit type. We call it a complementary since the final transistors is an NPN-PNP pair, each with the same characteristics. This circuit produce an AB class amplifier, since each transistor works in slightly more than half cycle of the signal. There is overlap area when both transistor conduct a current, and this area will be around its stationary current (when the input signal is zero). This circuit is also known as push-pull... Read Full Story

Interfacing high power load can be done in many ways, such as using voltage divider resistors, transformer, or optocoupler.  In the circuit shown below , an optocoupler method is presented. This optocoupler serve the logic level translation with flexible input, accepting wide range of voltage level, which is suitable for many high power load/devices. To couple a high-voltage load to a low-voltage logic input, this optocoupler basically convert the signal from the load (input) into light... Read Full Story

Sponsored Links Logic indicator circuit / logic probe is used to identify logic level at any point of logic circuitry. The indicator can be visual (using LED, LCD, of 7 Segments) or auditory (using beeper or speaker). This circuit has a audible indicator, with the help of  a loudspeaker to produce indication tone.  Using the opamp,U1, as schmitt trigger, the Audio oscillator Q3-Q1-Q2 is isolated from TTL. Beside that, the op amp also acts as high input impedance inverter. The R8-R9 is used... Read Full Story

Sponsored Links Ni-Cad (NiCd, NiCad) battery, sometimes doesn’t work as expected, gives no power and cannot be recharged. In this situation, the battery need to be reconditioned. It’ is possible that the battery is internally shorted, and we can get the battery into life again by recondition the Ni-Cad battery using a zapper circuit. This circuit restore the Ni-Cad battery from shorting by forcing a high current flow to burn the internal dirt. The current stored in the high capacitance... Read Full Story

Sponsored Links A Wien-Bridge oscillator circuit can be built from HA2541 and some basic components. This circuit can generate good-quality sine wave of 40 MHz with an upper limit of 50 MHz. The R3 through R7 and D2 and D1 provide the diode limiting for this circuit. Here is the schematic diagram of this circuit: For frequency stability, this circuit need a regenerative feedback. The feedback network is formed by R2/C2 and R1/C1. To obtain the oscillation, the gain required is three but... Read Full Story

Sponsored Links In automotive environment, it’s common that only single voltage power outlet is available. Using  the very popular LM317 voltage regulator IC, we can build a general purpose DC adapter to adapt car’s power outlet voltage (12-14 Volts) to supply small DC devices requiring lower voltage level. On the following schematic diagram for the car power adapter,  we can see that the output voltage depends on the value of R1, which is manipulated by connecting R3 or R4 via switch to... Read Full Story