LT6235 Linear Technology, LT6235 Datasheet - Page 24

• Manufacturer Part Number: LT6235
• Description: (LT6233 - LT6235) Op Amp Family
• Manufacturer: Linear Technology

LT6233/LT6233-10/
LT6234/LT6235
The LT6233 is applied as a transimpedance amplifier with
an I-to-V conversion gain of 10k set by R1. The LT6233
is ideally suited to this application because of its low input
offset voltage and current, and its low noise. This is be-
cause the 10k resistor has an inherent thermal noise of
13nV/ Hz or 1.3pA/ Hz at room temperature, while the
LT6233 contributes only 2nV and 0.8pA / Hz. So, with
respect to both voltage and current noises, the LT6233 is
actually quieter than the gain resistor.
The circuit uses an avalanche photodiode with the cathode
biased to approximately 200V. When light is incident on
PART NUMBER
LT1028
LT1677
LT1806/LT1807
LT6200/LT6201
LT6202/LT6203/LT6204
24
TYPICAL APPLICATIO S
RELATED PARTS
Low Power Avalanche Photodiode Transimpedance Amplifier
WWW.ADVANCEDPHOTONIX.COM
ADVANCED PHOTONIX
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] FAX: [phone]
012-70-62-541
OUTPUT OFFSET = 500 V TYPICAL
BANDWIDTH = 7.8MHz
OUTPUT NOISE = 1mV
200V BIAS
DESCRIPTION
Single, Ultra Low Noise 50MHz Op Amp
Single, Low Noise Rail-to-Rail Amplifier
Single/Dual, Low Noise 325MHz Rail-to-Rail Amplifier
Single/Dual, Low Noise 165MHz
Single/Dual/Quad, Low Noise, Rail-to-Rail Amplifier
0.1 F
I
10k
R2
C2
S
= 1.2mA
P–P
(20MHz MEASUREMENT BW)
–
+
U
LT6233
ENABLE
2.7pF
10k
R1
C1
www.linear.com
–5V
5V
623345 TA02a
the photodiode, it induces a current I
the amplifier circuit. The amplifier output falls negative to
maintain balance at its inputs. The transfer function is
therefore V
settling characteristics. Output offset was measured
at better than 500 V, so low in part because R2 serves to
cancel the DC effects of bias current. Output noise was
measured at below 1mV
bandwidth, with C2 shunting R2’s thermal noise. As shown
in the scope photo, the rise time is 45ns, indicating a signal
bandwidth of 7.8MHz.
COMMENTS
0.85nV/ Hz
2.5V Operation, 550 V Max V
0.95nV Hz, Rail-to-Rail Input and Output
1.9nV/ Hz, 3mA Max, 100MHz Gain Bandwidth
3V Operation, 2.5mA, 4.5nV/ Hz, 60 V Max V
Photodiode Amplifier Time Domain Response
OUT
= –I
PD
• 10k. C1 ensures stability and good
P–P
100ns/DIV
on a 20MHz measurement
LINEAR TECHNOLOGY CORPORATION 2003
OS
, 3.5nV/ Hz
LT/TP 1003 1K • PRINTED IN USA
PD
623345 TA02b
which flows into
OS
623345f