Tutorials

How the GSM system works?.

In various countries the frequency bandwidths specified for the GSM services are GSM-400, GSM-800, GSM-900, GSM-1800 and GSM-R.The GSM-900 and the GSM-1800 are the most widely used frequency bandwidths in different parts of the globe. The GSM-900 has a down link frequency range of 935-960 MHz and an up link frequency of range of 895-915 […]

Audio Circuits, Test & Measurement Circuits

Signal tracer circuit.

Description. A high gain amplifier circuit that can be operated from a battery pack of 6 or 9 volt battery pack is shown here.The IC1 uA 741 is wired as a high gain non-inverting amplifier and its output is amplified by a pair of complementary transistors (Q1 & Q2) to drive the speaker.The negative feedback

Audio Circuits

Guitar pre-amplifier using uA 741.

Description. A preamplifier circuit suitable for high impedance type electric guitar pickups is given here.The circuit is based on a uA 741 op-amp (IC1).The IC1 is wired as a non-inverting amplifier.The POT R1 can be used as a volume controller.The POT R6 can be used as tone controller.The switch S1 is used to produce “brilliant”

Tutorials

Introduction to PWM Inverters.

Nowadays most of the inverters available in the market utilizes the PWM(Pulse Width Modulation) technology.The inverters based on PWM technology are superior in many factors compared to other inverters designed using conventional technologies. The PWM based inverters generally use MOSFETs in the output switching stage.In such cases the inverters are generally termed as PWM MOSFET

Audio Circuits

Magnetic pickup pre-amplifier circuit.

Description. A preamplifier for magnetic pickups of record players is shown here.The uA 741 is used as an AC coupled non-inverting amplifier operating on a single supply.The amplifier gain is decided by the feedback components in which C2 controls the low frequency roll-off characteristics while C4 reduces the gain at high frequency end to compensate

Audio Circuits

Crystal pickup pre-amplifier circuit

Description. A preamplifier operating on a single supply and suitable for use with high impedance type crystal pickups is shown here.The circuit is basically a non-inverting AC amplifier in which the gain is dependent on the feedback resistor R4.The smaller is the R4,the lower will be the gain.The low frequency roll off characteristics are decided

Tutorials

How an Inverter works.

An inverter is used to produce an un-interrupted 220V AC or 110V AC (depending on the line voltage of the particular country) supply to the device connected as the load at the output socket. The inverter gives constant AC voltage at its output socket when the AC mains power supply is not available. Let’s look

Signal Conditioners, Test & Measurement Circuits

Schmitt trigger circuit using IC uA 741

Description. A Schmitt trigger circuit shows two distinct signal input levels for turning the circuit ON and OFF. The difference between the Von and Voff voltages called hysteresis Schmitt triggers are useful in converting slowly rising waveforms into fast rising ones and in relay like application. The circuit shown here uses a 741 with positive

Tutorials

Introduction to uA 741 Op-Amp

We have already discussed in detail about the basics on operational amplifier, its block diagram, symbol, different characteristics, and its circuit diagram (Refer:- Op Amps-Operational Amplifiers). In this post, we will be discussing about the 741 IC, one of the most popularly used op-amp IC. About the uA741 Op-amp IC The 741 IC was designed

Test & Measurement Circuits

Micro ampere meter circuit using uA 741

Description. The micro ampere meter shown here is basically a DC millivolt meter.The circuit gives full scale deflection for 0.1V input.The current to be measured is passed through a known resistance R and the voltage drop across it is measured.Here the IC 1 uA 741 op-amp is wired as a non inverting amplifier. Circuit diagram

Signal Generators

Square wave generator using uA 741

Square wave generator using uA741 opamp. uA 741 opamp IC. uA 741 is a very popular monolithic opamp IC that can be used for a lot of applications. The uA741 opamp was first introduced by Signetics and now a lot of manufacturers produce them. uA741 is commonly available in an 8 pin DIP plastic package

Home Circuits, Tone generator circuits

Door bell circuit using NE555

Description. The main part of this doorbell circuit are two NE555 timer ICs.When some one presses switch S1 momentarily, the loud speaker sounds a bell tone as long as the time period of the monostable multivibrator built around IC1. When the switch S1 pressed, IC1 is triggered at its pin 2 and output pin 3

Test & Measurement Circuits

Voltage follower circuit

Description. An AC coupled unity gain  gain voltage follower operating on a single supply is shown here.The voltage divider network of R1 and R2 provides a DC voltage equal to half the supply voltage to the non-inverting input of the 741.The output DC voltage therefore stands at half the supply voltage.The output signal swings above

Audio Circuits, Industrial Circuits

Power megaphone circuit

Description. Just about any power transistor can be used in  this megaphone.Its suitable for boats,playing fields etc.the transistors Q1  & Q2 are the HEP-230 type which are easily available in the market.The transistors are parallely connected to handle the required power and speaker matching.The microphone is a carbon type like that used in telephone hand

Fun & Game Circuits

Sense of Time tester circuit.

Description. When S2 is ON ,the circuit here operates as an astable multi vibrator and the LED is lit for about o.1sec,flasing every 1.5 seconds.Since the human reaction time is more than this,you cannot catch it once it is seen o,by pressing S1.If your sense of time interval is good,and you press S1 with in

Signal Conditioners

Scmitt Trigger circuit using NE 555

Description. Apart from the timing functions ,the two comparators of the 555 timer can be used independently for other applications.One example is a Schmitt Trigger shown here. The two comparator inputs (pin 2 & 6) are tied together and biased at 1/2 Vcc through a voltage divider R1 and R2.Since the threshold comparator wil trip

Power Supplies

12 V High current regulator

Description. This voltage regulator circuit can deliver up to 3A at 12V output voltage. The circuit can be employed on occasions when a current of more that 3A is demanded for regulator. IC regulators of such high current rating are pretty hard to find. The transformer T1 steps down mains voltage, to 12rms & the

Test & Measurement Circuits

555 Tester circuit

Description. NE555 is an IC which is widely used in timers and control circuits. A circuit for independent testing this IC is given here. Here the NE555 is wired as an astable multivibrator. When the push button switch S1 is pressed the LEDs D1 & D2 will flash alternatively. That is when output is high

Power Supplies

Regulated power expander circuit

Description. Commercially available voltage regulator IC’s can deliver up to 1A output current. For example 78xx series regulators are available in different voltage ratings, but in any case the current should not exceed 1A. The transistor Q1 (2N 29055) used here has 5A current capacity. The resistor R1 is used to keep the current through

Automotive Circuits

Head light timer circuit

Description. This circuit is a compact timer circuit that will keep the headlights of your car ON for about 1.5 minutes and then turns it OFF.This circuit incorporated to your car will help you to access dark places with out the need to come back and turn OFF the head lights. When the push button

Automotive Circuits, Home Circuits, Lighting Circuits

Lamp flasher circuit

Description. This simple circuit that can be used to flash incandescent lamps up to 10W power rating.The circuit is ideal for making flashing beacons on automobiles and other applications like that.The circuit is nothing but  an astable multi vibrator based on Q1&Q2 ( BC557&BD139).The capacitor C1 is the main timing element which determines the flashing

Industrial Circuits, Tone generator circuits

Electronic siren circuit

Description. This is a compact electronic siren circuit based on three transistors.This circuit is suitable for in corporating with other alarm or siren projects such as burglar alarms, automatic factory sirens etc or a simple push to on alarm. The  electronic siren circuit given here  is  based on a complementary transistor pair consisting of Q2

Home Circuits, Sensor Circuits

Water level alarm circuit

Description. Here is a simple water level alarm circuit using 555 timer that will produce an audible alarm when the water level reaches  a preset level.The circuit can be powered of a  3V battery and is very handy to use. The circuit is based on an astable multivibrator wired around IC1 (NE 555).The operating frequency

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