H11F3SM Datasheet, PDF (6/11 Pages) Fairchild Semiconductor – Photo FET Optocouplers

Typical Applications
As a Variable Resistor
ISOLATED VARIABLE ATTENUATORS
As an Analog Signal Switch
ISOLATED SAMPLE AND HOLD CIRCUIT
500K
V_IN
I_F
V_OUT
H11F1M
V_IN
H11F1M
I_F
50 VOUT
LOW FREQUENCY
@10KHz ^{DYNAMIC RANGE 70db}
FOR 0 ≤ IF ≤ 30mA
HIGH FREQUENCY
@1MHz ^{DYNAMIC RANGE 50db}
FOR 0 ≤ IF ≤ 30mA
Distortion free attenuation of low level A.C. signals is accom-
plished by varying the IRED current, I_F Note the wide dynamic
range and absence of coupling capacitors; D.C. level shifting or
parasitic feedback to the controlling function.
V_IN
H11F1M
I_F
+
-
C
V_IN
V_OUT
I_F
V_OUT
t
Accuracy and range are improved over conventional FET
switches because the H11FXM has no charge injection from
the control signal. The H11FXM also provides switching of
either polarity input signal up to 30V mag.nitude.
AUTOMATIC GAIN CONTROL
V_IN
H11F1M
I_F
AGC
SIGNAL
+
-
500K
V_OUT
MULTIPLEXED, OPTICALLY-ISOLATED A/D CONVERSION
CALL V1
H11F1M
CALL
V_n
DATA
V₁
H74A1
ACQUISITION
V₂
MSB
MSB
A/D
PROCESS
CONVERTER
CONTROL
V_n
LSB ^H74A1
LOGIC
SYSTEM
LSB
H11F1M
This simple circuit provides over 70db of stable gain control for
an AGC signal range of from 0 to 30mA. This basic circuit can
be used to provide programmable fade and attack for electronic
music.
The optical isolation, linearity and low offset voltage of the
H11FXM allows the remote multiplexing of low level analog signals
from such transducers as thermocouplers, Hall effect devices,
strain gauges, etc. to a single A/D converter.
ACTIVE FILTER FINE TUNING/BAND SWITCHING
I_F1
I_F2
H11F1M
H11F1M
TEST EQUIPMENT - KELVIN CONTACT POLARITY
H11F1M
H11F1M
I_F
I_F
A1
A2
A3
A
I_TEST
DEVICE
UNDER
TEST
B
C
PARAMETER
SENSING
BOARD
I_F TO
A & B FOR
POLARITY 1
C & D FOR
POLARITY 2
D
I_F1 ADJUSTS f₁, I_F2 ADJUSTS f₂
The linearity of resistance and the low offset voltage of the
H11FXM allows the remote tuning or band-switching of active
filters without switching glitches or distortion. This schematic
illustrates the concept, with current to the H11F1M IRED’s
controlling the filter’s transfer characteristic.
I_F
I_F
H11F1M
H11F1M
In many test equipment designs the auto polarity function uses
reed relay contacts to switch the Kelvin Contact polarity. These
reeds are normally one of the highest maintenance cost items
due to sticking contacts and mechanical problems. The totally
solid-State H11FXM eliminates these troubles while providing
faster switching.
©2007 Fairchild Semiconductor Corporation
H11F1M, H11F2M, H11F3M Rev. 1.0.5
6
www.fairchildsemi.com