MT88L70
Differential Input Configuration
Data Sheet
The input arrangement of the MT88L70 provides a differential-input operational amplifier as well as a bias source
(V
Ref
) which is used to bias the inputs at mid-rail. Provision is made for connection of a feedback resistor to the op-
amp output (GS) for adjustment of gain. In a single-ended configuration, the input pins are connected as shown in
Figure 6 with the op-amp connected for unity gain and V
Ref
biasing the input at 1/2V
DD
. Figure 5 shows the
differential configuration, which permits the adjustment of gain with the feedback resistor R
5
.
C
1
R
1
IN+
+
-
IN-
MT88L70
C
2
R
4
GS
R
3
R
2
R
5
V
Ref
DIFFERNTIAL INPUT AMPLIFIER
C
1
= C
2
= 10 nF
All resistors are
±
1% tolerance.
R
1
= R
4
= R
5
= 100 kΩ
All capacitors are
±
5% tolerance.
R
2
= 60 kΩ, R
3
, = 37.5 kΩ
R
2
R
5
R
3
=
R
2
+ R
5
R5
VOLTAGE GAIN (A
V
diff) =
R1
INPUT IMPEDANCE
(Z
INDIFF
) = 2
R
12
+
1
ωC
2
Figure 5 - Differential Input Configuration
Crystal Oscillator
The internal clock circuit is completed with the addition of an external 3.579545 MHz crystal and is connected as
shown in Figure 6 (Single-ended Input Configuration).
6
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
