The Unity-Gain Buffer - Freecircuits.net

Electronic circuits schematics diagrams FreeCircuits.net [category-12.html] The Unity-Gain Buffer By internum The circuit gives the highest input impedance of any operational amplifier circuit. The unity-gain buffer is shown in Figure 1. The circuit gives the highest input impedance of any operational amplifier circuit. Input impedance is equal to the differential input impedance multiplied by the open-loop gain, in parallel with common mode input impedance. The gain error of this circuit is equal to the reciprocal of the amplifier open-loop gain or to the common mode rejection, whichever is less. Figure 1. Unity Gain Buffer VOUT = VIN R1 = RSOURCE For minimum error due to input bias current Input impedance is a misleading concept in a DC coupled unity-gain buffer. Bias current for the amplifier will be supplied by the source resistance and will cause an error at the amplifier input due to its voltage drop across the source resistance. Since this is the case, a low bias current amplifier such as the LH1026 should be chosen as a unity-gain buffer when working from high source resistances. The cautions to be observed in applying this circuit are three: the amplifier must be compensated for unity gain operation, the output swing of the amplifier may be limited by the amplifier common mode range, and some amplifiers exhibit a latch-up mode when the amplifier common mode range is exceeded. The LM107 may be used in this circuit with none of these problems; or, for faster operation, the LM102 may be chosen. 1 09 December 2007 See also: Differentiator Differentiator and Practical Differentiator. Triangle-Wave Generator This circuit provides a variable frequency triangular wave whose amplitude is independent of frequency. Summing Amplifier The summing amplifier, a special case of the inverting amplifier. Home Audio Video & TV Power RF Digital Computer Telephone Measurement Security Lights & LED Oscillators Op Amplifiers Other Search Copyright © 2007 freecircuits.net