Adjustable Voltage References - Freecircuits.net

Electronic circuits schematics diagrams FreeCircuits.net [category-12.html] Adjustable Voltage References By internum Adjustable voltage reference circuits (Positive and Negative). Adjustable voltage reference circuits are shown in Figures 1, 2, 3, 4. The two circuits shown have different areas of applicability. The basic difference between the two is that Figures 1, 2 illustrate a voltage source which provides a voltage greater than the reference diode while Figures 3, 4 illustrates a voltage source which provides a voltage lower than the reference diode. The figures show both positive and negative voltage sources. Figure 1. Positive Voltage Reference High precision extended temperature applications of the circuit of Figures 1, 2 require that the range of adjustment of VOUT be restricted. When this is done, R1 may be chosen to provide optimum zener current for minimum zener T.C. Since IZ is not a function of V+, reference T.C. will be independent of V+. Figure 2. Negative Voltage Reference The circuit of Figures 3, 4 are suited for high precision extended temperature service if V+ is reasonably constant since IZ is dependent on V+. R1, R2, R3, and R4 are chosen to provide the proper IZ for minimum T.C. and to minimize errors due to Ibias. Figure 3. Positive Voltage Reference The circuits shown should both be compensated for unity-gain operation or, if large capacitive loads are expected, should be overcompensated. Output noise may be reduced in both circuits by bypassing the amplifier input. Figure 4. Negative Voltage Reference The circuits shown employ a single power supply, this requires that common mode range be considered in choosing an amplifier for these applications. If the common mode range requirements are in excess of the capability of the amplifier, two power supplies may be used. The LH101 may be used with a single power supply since the common mode range is from V+ to within approximately 2 volts of V−. 3 10 December 2007 See also: Tracking Regulated Power Supply This supply is very suitable for powering an operational amplifier system since positive and negative voltages track. Low Drift Sample and Hold circuit A sample-and-hold circuit which combines the low input current of FETТs with the low offset voltage of monolithic amplifiers. Sine Wave Oscillator An amplitude-stabilized sine-wave oscillator. This circuit provides high purity sine-wave output down to low frequencies with minimum circuit complexity. Home Audio Video & TV Power RF Digital Computer Telephone Measurement Security Lights & LED Oscillators Op Amplifiers Other Search Copyright © 2007 freecircuits.net