Transistor Buffer

Measurements PART II

(Differential Input, ~100mA Iq)

Measurements:

Opamp	2nd harm.	3rd harm.	others
LME49720 (no PreLowPass)	- 133 dB / 2.1 kHz	-125.0 dB / 3.15 kHz	none
LME49720 (PreLowPass 1kHz)	< -135dB / 2.1 kHz	-117.0 dB / 3.15 kHz	-127.5 dB / 1.74 kHz
AP-SYS 2	-127.5dB / 2 kHz	-132.0 dB / 3 kHz	none

1. Lowpass adds 3rd harmonic
2. AP-SYS2 Input stage generates 2nd harmonics

As in APWIN programm shown, minimal range for the level meters is 40mV.
The external (self build) notch rejects fundamental by 45 dB (~ 1/180), resulting in  ~ 11mV for 2V input (5.5mV for 1V).
Therefore, ~ 11 dB of resulation (in FFT) will be lost if notch results are not externally amplified (to test: 20dB)

Link to OPA134
Link to LME49720
Link to AP-SYS2

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Notch frequency response (zoomed)

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OPA2134, 1Vrms, 27 Ohms, NotchFilter 1kHz, No Lowpass, Notch NOT amplified



OPA2134, 1Vrms, 27 Ohms, NotchFilter 1kHz, Lowpass 1kHz, Notch NOT amplified

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LME49720, 1Vrms, 27 Ohms, NotchFilter 1kHz, Lowpass 1kHz, Notch NOT amplified



LME49720, 1Vrms, 27 Ohms, NotchFilter 1kHz, NO Lowpass, Notch NOT amplified







LME49720, 2Vrms, 27 Ohms, NotchFilter 1kHz, NO Lowpass, Notch NOT amplified, zoomed




LME49720, 2Vrms, 27 Ohms, NotchFilter 1kHz,  Lowpass 1kHz , Notch NOT amplified, zoomed

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AP SYS2


AP SYS2, FFT Generator 1V, after Notch