A peak detector for implementation in a monolithic integrated circuit includes one or more Miller capacitors and one or more transistors for selectively setting large RC time constant values only with components included in the integrated circuit's die. Neither resistors nor capacitors located outside the integrated circuit are used for setting a selected value of a time constant. Some embodiments of the invention include diodes for compensation of amplifier leakage current in the peak detector, thereby increasing a maximum value of a time constant that can be implemented in an integrated circuit. A peak detector in accord with an embodiment of the invention may optionally be configured for either single-ended or differential operation.