Precision Op-Amp Current Source

In this circuit we tackle the error indicated in the earlier Current Source. The LM336-2.5V eliminates the tiny error of the regulated supply and resistors. Thereby increasing Precision to a higher degree.

The opamp mirrors the stable 2.5V across P3 + R13. With P3 Bourns 10 Turn Trimpot you can trim the current for calibration. Q1 BC557B having a Beta – hfe of 200 is used. But a higher gain or a FET here may reduce error further, that may be needed if you are going for 16 Bit or more resolution. Then even opamp needs to change.

Mini RTD Pt-100 Three Wire Transmitter

Suppose you build it with the best Opamp, FET etc., but place it close to a Warm transformer, Regulator chip or even a Cooling Fan, you will see the lower digits of a 5-1/2 DMM spinning fast.

  • Fixed frequency Variable duty cycle with 555Fixed frequency Variable duty cycle with 555
    This circuit is based on a very old application note from exar, in this the frequency is fixed by IC1 and IC2 -P1 controls the [...]
  • Simple Mains Voltage monitorSimple Mains Voltage monitor
    This Circuit helps in the monitoring of mains supply voltage. It does not use a isolation step down transformer. This has to be constructed only [...]
  • InfraRed Detector for Proximity SwitchInfraRed 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 [...]
  • Isolated dual power supply from 5VIsolated dual power supply from 5V
    This is a unregulated supply for low power circuits. You may be able to regulate the outputs with zeners or small regulators like 78L05. The [...]
  • AD590 based Temperature SensorAD590 based Temperature Sensor
    Learn how to use the AD590 to measure environment temperatures for display, logging or cold junction compensation. The voltage at the point 1 of R4 [...]
  • Simple High speed data switchSimple High speed data switch
    This circuit is a small representation of a very low cost printer sharer. It has no Active Devices only diodes. Pot the product in epoxy [...]
  • Microohm Meter with LED Analog BarMicroohm Meter with LED Analog Bar
    This indicates like LM3914 in dot-mode. It is a drawing i made made to troubleshoot a gadget, around two decades ago. Strangely it had a [...]
  • Amp Hour Meter using LM331 and 74C926Amp Hour Meter using LM331 and 74C926
    LM331 is a Voltage-to-Frequency Converters and  74C926 is a 4 Digit Counter. The first part of the circuit converts the amplified DC analog value from [...]
About delabs 152 Articles
Product Design - Industrial Automation and Instrumentation. -

Be the first to comment

Leave a Reply