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Datasheet A2TPMI
OUTPUT SIGNAL
The A2TPMI amplifiers are realized in chopper amplifier technology. Due to the nature of this technol-
ogy the output signals VTobj and VTamb incorporate an AC signal of approximately 10 mV peak to peak in
the range of 250 kHz. This AC voltage can be suppressed either by an electrical low pass filter or via an
additional software filtering.
In applications with low resistive load ( > 1Mohm) a simple RC low pass filter as follows can be used to
smooth the signal:
500 Ohms
A2TPMI
VTobj or VTamb
VTobj or VTamb filtered
L1 Option
³470 nF
In applications with high resistive load (50kOhm … 1MOhm) filtering can be achieved with the following
circuit. A rail to rail OPAmp like the LMV358 should be used so that the full sensing range will be avail-
able on the output of the filter circuit.
C
L2 Option
LMV358
R
R
A2TPMI
VTobj or VTamb
+
VTobj or VTamb filtered
C
R = 10kOhms
C = 100nF
PRINTED CIRCUIT BOARD (PCB) VERSION
Two different sizes of standard PCB versions are available. P1 version is a 17 x 34 mm2 PCB which
allows assembly of additional external mirror optics (M options). P3 version is 17 x 20 mm2 PCB suit-
able for applications with restricted space. P3 version is not available with mirror (M option).
Each PCB version is available either as plain version (sensor directly wired to connector), or with 1st
order (RC-circuit, L1 option) or 2nd order (active OpAmp circuit, L2 option) low pass filter, in order to
provide attenuation of the AC portion on the output signal as described in chapter Output Signal.
A2TPMI Datasheet Rev4
Page 12 of 21
Rev. Oct 2003
PERKINELMER [ PERKINELMER OPTOELECTRONICS ]
