Description

Electrical schematics

Prototype measurements

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Peak detector: gain measurements

The peak detector prototype has been tested applying to its input a 1 MHz sinewave whose amplitude has been varied, ranging from 5 mV rms to 1,5 V rms.

The maximum allowable input signal has not been checked, but it can be considered to be around 10 V rms (sinewave), taking into account the op-amp characteristics and power supply value.

All signals have been measured with a LeCroy mod. 9310A digital storage oscilloscope; rms measurements given below have been directly evaluated by the instrument, internally processing its measured signals samples.

The following table lists, for each applied input signal:

1. Nominal value of the input signal (V_IN), expressed in volts rms.
2. Effective (measured) input signal (V_INrms), expressed in volts rms.
3. Calculated input signal peak value (V_INpk), expressed in volts peak; i.e.:V_INrms multiplied by the square root of 2.
4. Output DC level (V_OUTdc), expressed in volts.
5. Detector gain, evaluated as V_OUTdc / V_INpk ratio, given as a number.
6. Detector gain error with respect to unity gain, expressed in dB.

Ideal gain should be always 1, no matter the input signal level; in the real world it ranges from slightly less than 0,29 (for V_IN =5 mVrms) up to a peak of 1,13 (for V_IN =100 mVrms), back to slightly less than 1 for higher input levels.

Speaking of gain error, expressed in decibels, the unit performs as follows.

• The minimum input level that gives a -3 dB gain error is less than 30 mV rms;
• With a 50 mV rms input signal, gain error is +0,065 dB;
• With a 100 mV rms input signal the maximum gain peaking is found, giving a gain error of 1,076 dB;
• With input signals greater than 300 mV rms gain error remains within ± 0,2 dB.

Data ultimo aggiornamento 26/06/99
Aggiornato da Piero Montanari
Indirizzo di posta elettronica: bin8829@iperbole.bologna.it