Voltage to Current Source 4-20 mA

 Opamp-Circuits  No Responses »
Feb 162009
 
Voltage to Current Source 4-20 mA

The 0-1V to 4-20 mA Converter published earlier is a current sink, Here is a circuit that is a voltage to current converter but with a current source. You can use a LM358 or LM324. The first opamp is a Voltage to Current with a sink output. That current creates a varying voltage w.r.t the 12V DC supply, this varying voltage is mirrored by the second opamp across the source output resistor. This way a constant current is obtained with a sourcing output. The control elements are small signal high gain transistors. Any suitable equivalent can be used. Even the Read More …

 Posted by admin at 12:50 AM  Tagged with:

Diode Reverse Bias Leakage Tester

 Opamp-Circuits, Test-Measurement  No Responses »
Dec 232008
 
Diode Reverse Bias Leakage Tester

This is a Test arrangement for Leakage Testing of Diodes on Reverse Bias. The leakage current indicates the ability of the diode to withstand higher voltages. An AutoTransformer or Variac can be used to vary the test voltage. Even Plastic capacitors can be tested for leakage this way. Safety Precautions – Use a Isolation 1:1 transformer for safety. This circuit has to be enclosed in a insulated cabinet. A Jig or Acrylic Safety Plate with clamp can be used to connect the diode. The voltage is only applied as long as a Mains two way push switch is pressed. This Read More …

 Posted by admin at 10:35 PM

Dual Polarity Analog Output Op-Amps

 Opamp-Circuits  No Responses »
Dec 152008
 
Dual Polarity Analog Output Op-Amps

When you have to buffer and invert the polarity of mV input levels. This is the circuit you can use, as OP07 has uV offset. R9 and R10 can be 100K 1% MFR or better. Use a symmetrical dual supply. OP07: Ultralow Offset Voltage Operational Amplifier

 Posted by admin at 9:30 PM

Precision Amplifier with Digital uC Control

 Embedded-Systems, Opamp-Circuits, Test-Measurement  No Responses »
Dec 152008
 
Precision Amplifier with Digital uC Control

When Instruments are designed a analog front end is essential and also as most equipment have digital or microcontroller interface the analog circuit needs to have digital access. The Circuits DACT0008 and DACT0009 are both useful in building instruments which have digital control. This circuit DACT0009 is similar to DACT0008 but gains of upto 100 can be realized in this configuration, this is useful for signal conditioning of low mV outputs of transducers. The gain selection resistors R3 to R6 can be selected by the user and can be anywhere from 1K to 1M and can also be trimpots for Read More …

 Posted by admin at 4:45 AM

InfraRed Detector for Proximity Switch

 LED-Circuits, Opamp-Circuits  No Responses »
Dec 142008
 
InfraRed Detector for Proximity Switch

The proximity switch can work for a wide range of power, from 8v to 18v DC, D3 protects reverse power supply connections, and U1 regulates the supply to +5v , -5v is derived from U2 555 oscillator which serves dual purpose. Circuit Operation The infra red diode D2 detector gets the reflected light from LED and some ambient light, The forward voltage drop of D2 will vary with the amount of light falling on it. Ambient light causes a DC component and the pulsing light from D1 causes an AC component. The capacitor C6 blocks DC and only transfers AC Read More …

 Posted by admin at 3:00 AM

Precision Attenuator for Digital uC Control

 Embedded-Systems, Opamp-Circuits, Test-Measurement  No Responses »
Dec 102008
 
Precision Attenuator for Digital uC Control

When Instruments are designed a analog front end is essential and also as most equipment have digital or microcontroller interface the analog circuit needs to have digital access. The Circuits DACT0008 and DACT0009 are both useful in building instruments which have digital control. Precision Attenuator with digital control The Circuit DACT0008 is a programmable attenuator and the digital control can be a remote dip switch, a CMOS Logic Output like the A-B-C-D outputs of a decade counter, or an I/O port of a uC like 80C31. The heart of the circuit is the popular OP07 OpAmp with Ultra Low Offset Read More …

 Posted by admin at 6:25 PM

Square and Triangle Opamp Oscillator

 Opamp-Circuits  No Responses »
Oct 212008
 
Square and Triangle Opamp Oscillator

Here is the circuit of a Op-Amp based Square Wave Generator. One of the main application of this is in a Simple PWM circuit and Triangle Opamp Oscillator. The Slope of the Triangle wave is compared with a DC Level to derive a pulse width or On-Time proportional to a Voltage. This On-Time proportional to voltage is for a fixed oscillation rate based on C2-C3 and R15. The C2-C3 form a Unpolarized cap, This type is also used in crossover networks in speaker boxes. This is because, a plastic 4.7 uF (2 * 10uF series) is big and costlier, but Read More …

 Posted by admin at 11:21 PM  Tagged with:
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