26-11-2012, 06:32 PM
rectifier
rectifiers.docx (Size: 104.42 KB / Downloads: 20)
Nonlinear op-amp circuits:
• Most typical applications require op amp and its components to act linearly
– I-V characteristics of passive devices such as resistors, capacitors should be described by linear equation (Ohm’s Law)
– For op amp, linear operation means input and output voltages are related by a constant proportionality (Av should be constant)
• Some application require op amps to behave in nonlinear manner (logarithmic and antilogarithmic amplifiers)
Logarithmic Amplifier
• Output voltage is proportional to the logarithm of input voltage
• A device that behaves nonlinearly (logarithmically) should be used to control gain of op amp
– Semiconductor diode
Precision Rectifiers
• Useful when signal to be rectified is very low in amplitude and where good linearity is needed
• Frequency and power handling limitations of op amps limit the use of precision rectifiers to low-power applications (few hundred kHz)