OPT101_03 BURR-BROWN [Burr-Brown Corporation], OPT101_03 Datasheet - Page 9

• Manufacturer Part Number: OPT101_03
• Description: MONOLITHIC PHOTODIODE AND SINGLE-SUPPLY TRANSIMPEDANCE AMPLIFIER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

DARK ERRORS
The dark errors in the specification table include all sources.
The dominant source of dark output voltage is the “pedestal”
voltage applied to the non-inverting input of the op amp.
This voltage is introduced to provide linear operation in the
absence of light falling on the photodiode. Photodiode dark
current is approximately 2.5pA and contributes virtually no
offset error at room temperature. The bias current of the op
amp's summing junction (– input) is approximately 165pA.
The dark current will be subtracted from the amplifier's bias
current, and this residual current will flow through the
feedback resistor creating an offset. The effects of temperature
on this difference current can be seen in the typical
performance curve “(I
dark output voltage can be trimmed to zero with the optional
circuit shown in Figure 3. A low impedance offset driver (op
amp) should be used to drive pin 8 because this node has
signal-dependent currents.
CHANGING RESPONSIVITY
An external resistor, R
voltage responsivity. To increase the responsivity, this resistor
can be placed in series with the internal 1M (Figure 4a), or
the external resistor can replace the internal resistor by not
connecting pin 4 (Figure 4b). The second configuration also
allows the circuit gain to be reduced below 10
external resistors of less than 1M .
Figure 4 includes tables showing the responsivity and
bandwidth. For values of R
capacitor, C
OPT101
FIGURE 3. Dark Error (Offset) Adjustment Circuit.
SBBS002A
Common
EXT
2
should be connected in parallel with R
OPA177
8
+15V
–15V
EXT
V
BIAS
B
, can be connected to set a different
– I
3
F
–V
DARK
1
1M
less than 1M , an external
V
S
OPT101
3pF
8pF
–15V
) vs Temperature.” The
500k
1/2 REF200
R
1
100 A
4
5
with no light.
for V
Adjust R
6
V/A by using
O
= 0V
V
O
1
www.ti.com
F
.
This capacitor eliminates gain peaking and prevents
instability. The value of C
table in Figure 4. Values of R
can be interpolated.
FIGURE 4. Changing Responsivity with External Resistor.
Note: (1) May require 1k in series with pin 5 when driving
large capacitances.
0.05
R
(M )
R
(M )
0.1
10
50
10
50
EXT
1
2
5
EXT
1
2
5
(1)
(1)
2
2
8
C
C
(pF)
(pF)
50
25
10
—
56
33
—
—
—
—
—
EXT
8
EXT
5
(b)- External Feedback
V
B
(a)- Series R
V
B
EXT
F
3
(x10
(x10
, other than shown in the table,
DC Gain
DC Gain
3
can be determined from the
1M
1
0.05
0.1
V
11
51
10
50
2
3
6
1
1M
1
2
5
6
6
C
R
S
V/A)
V
V/A)
OPT101
EXT
3pF
EXT
EXT
8pF
S
OPT101
3pF
8pF
Bandwidth
R
Bandwidth
4
5
EXT
4
5
(kHz)
(kHz)
0.34
0.33
9.4
3.6
1.8
2.5
1.3
58
44
23
8
6
C
EXT
9