Simple 4 Channel Commutator Circuit

This is design circuit for commutator circuit. This circuit is simplest form. The circuit is built by four FET that can be use for 4 channels. This is the figure of the circuit;

To reach low channel ON resistance (<30 Ohm) and low OFF current leakage, 4-channel commutator uses the 2N4091. The DM7800 voltage translator is a monolithic device. This devices give us +10V to -20V gate drive to the JFETs while at the same time giving DTL-TTL logic compatibility.

Simple Step-up PWM DC-DC Converter Integrated with 4 Buffers

This is a circuit for converter that is a simple form for DC to DC Converter circuit. This circuit is based on LM2711 from National Semiconductor. This is the figure of the circuit;

The LM2711 has a current mode PWM step-up DC/DC converter with a 1.4A, 0.17 internal switch. Capable of generating 8V at 300mA from a Lithium Ion battery, the LM2711 is ideal for generating bias voltages for large screen LCD panels. The LM2711 can be operated at switching frequencies of 600 KHz or 1.25MHz, allowing for easy filtering and low noise. An external compensation pin gives the user flexibility in setting frequency compensation, which makes possible the use of small, low ESR ceramic capacitors at the output. The LM2711 uses a patented internal circuitry to limit startup inrush current of the boost switching regulator without the use of an external soft start capacitor. An external soft start pin enables the user to tailor the soft start to a specific application. The LM2711 contains 4 Gamma buffers capable of supplying 50mA source and sink. The TSSOP-20 package ensures a low profile overall solution. [Schematic circuit source: National Semiconductor Notes]

Simple Precision Power Regulator Circuit

Making a precision voltage source is easy, but not so easy if the voltage should be consistent over wide range of ambient temperature. Such requirement might be needed in high precision measurement system, for providing reference voltage in analog to digital conversion for example. This is a design circuit for precision power regulator. This is the figure of the circuit;

This circuit is based on LM 336. LM336 voltage references are easier to use than zener diodes. Their low impedance and wide current range facilitate biasing in any circuits. Besides, the breakdown voltage or the temperature coefficient can be adjusted so as to optimize the performance of the circuit. [Circuit diagram source: STMicroelectronics Application Note]

Simple Analog Multiplier Circuit

This is a circuit for a simple embodiment of the analog multiplier. This circuit provides three quadrant analog multiplication which is relatively temperature insensitive and which is not subject to the bias current errors which is plague most multipliers and circumvents many of the problems associated with the log-antilog circuit. This is the figure of the circuit;

By considering A2 as a controlled gain amplifier, amplifying V2, whose gain is dependent on the ratio of the resistance of PC2 to R5 and by considering A1 as a control amplifier which establishes the resistance of PC2 as function of V1, circuit operation may be used. It is seen that Vout is a function of both V1 and V2 in that way. Drive for the lamp L1 is provided by the control amplifier(A1). L1 is driven by A1 until the current to the summing junction from the negative supply through PC1 is equal to the current to the summing junction from V1 through R1 when an input voltage (V1) is present. This forces the resistance of PC1 to a value proportional to R1 and the ratio of V1 to V- since the negative supply voltage is fixed. L1 also illuminates PC2 and causes PC2 to have a resistance equal to PC1 if the photoconductors are matched. The controlled amplifier (A2) behaves as an inverting amplifier whose gain is equal to the ratio of the resistance of PC2 to R5. Vout becomes simply the product of V1 and V2 if R5 is chosen equal to the product of R1 and V-. To provide any required output scale factor, R5 may be scaled in powers of ten.

Since the T.C. of resistance is related to resistance match for cells of the same geometry, PC1 and PC2 should be matched for best tracking over temperature. Varying the value of R5 as a scale factor adjustment is used to compensate small mismatches. The photoconductive cells should receive equal illumination from L1, a convenient method is to mount the lamp midway between them. Controlled spacing and a thermal bridge between the two cells to reduce differences in cell temperature is provided by this mounting method. To the use of FET’s or other devices to meet special resistance or environment requirements, we can extend this technique.

An inverting output whose magnitude is equal to one-tenth the product of the two analog inputs is given on this circuit. Positive value is restricted for input V1 but V2 may assume both positive and negative value. By the lamp time constant, his circuit is restricted to low frequency operation. To minimize errors due to input offset current as outlined in the section describing the photocell amplifier, R2 and R4 are chosen. To reduce in-rush current when firdt turning on the lamp (L1), R3 is included.

[Circuit source: National Semiconductor Notes]

Simple Microphone Amplifier Circuit

This is a circuit diagram of a device which can hear faint sounds and those sounds which any normal microphone can not hear. This is a very useful circuit and one can use this circuit for many tasks this circuit can be used as a hearing aid. Use direct coupling and do not use bulky coupling or bypass capacitors. The circuit using only a few components the size of the circuit is very small so one can easily fit it in a small box. This is the figure of the circuit;

Capacitor 1 bypasses ac negative feedback due to which the gain is not affected. Q1, Q2 and Q3 are bc 337. Resistor 1 is used for volume control. Transistor 1, transistor 2 and transistor 3 all are direct coupled amps. Their operation is stabilized by direct current (DC) negative feed back through resistor 4.

Simple Loud Hailer Circuit

This is a simple and useful circuit project of loud hailer the circuit uses only one transistor connected with transformer which puts out a loud sound. The circuit can be easily fixed in a metal package with the speaker mounted on the top. Heat sink is essential for the transistor or it will burn out, fix the circuit in metal package and also use this metal package as heat sink of transistor. This is the figure of the circuit;

Use carbon mic or telephone mic/telephone transmitter element. The circuit can be build inside of a speaker trumpet like the loudhailers available in market. Make sure that the mic is isolated from the speaker to prevent feedback. Use the transformer which will able to provide 5 watt output power.

Simple Lie Detector Circuit

If you want to know someone is lying or not we can use lie detector. This is a simple lie detector that can be made in minutes. It works to detect someone who telling lie but it is not as sophisticated as the ones the professionals use. This is the figure of the circuit;

The skin resistance will go down when someone telling lie and this circuit works by measuring it. We can use electrode pads, alligator clips, or just wires and tape as the electrodes. We have to adjust R2 to position the meter at the center at the beginning of the interrogation (relax condition), then we can know someone is lying when the meter changes in response to a question.

[Schematic circuit source: aaroncake.net]