Datasheet
LT6233/LT6233-10
LT6234/LT6235
24
623345fc
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2003
LT 0111 REV C • PRINTED IN USA
relaTeD parTs
Typical applicaTions
Low Power Avalanche Photodiode Transimpedance Amplifier
I
S
= 1.2mA
Photodiode Amplifier Time Domain Response
PART NUMBER DESCRIPTION COMMENTS
LT1028 Single, Ultralow Noise 50MHz Op Amp 0.85nV/√Hz
LT1677 Single, Low Noise Rail-to-Rail Amplifier 3V Operation, 2.5mA, 4.5nV/√Hz, 60µV Max V
OS
LT1806/LT1807 Single/Dual, Low Noise 325MHz Rail-to-Rail Amplifier 2.5V Operation, 550µV Max V
OS
, 3.5nV/√Hz
LT6200/LT6201 Single/Dual, Low Noise 165MHz 0.95nV√Hz, Rail-to-Rail Input and Output
LT6202/LT6203/LT6204 Single/Dual/Quad, Low Noise, Rail-to-Rail Amplifier 1.9nV/√Hz, 3mA Max, 100MHz Gain Bandwidth
The LT6233 is applied as a transimpedance amplifier with
an I-to-V conversion gain of 10kΩ set by R1. The LT6233
is ideally suited to this application because of its low in-
put offset voltage and current, and its low noise. This is
because 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
the photodiode, it induces a current I
PD
which flows into
the amplifier circuit. The amplifier output falls negative
to maintain balance at its inputs. The transfer function
is therefore V
OUT
= –I
PD
• 10k. C1 ensures stability and
good settling characteristics. Output offset was measured
at better than 500µV, so low in part because R2 serves to
cancel the DC effects of bias current. Output noise was
measured at below 1mV
P-P
on a 20MHz measurement
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.
+
–
R1
10k
R2
10k
C2
0.1µF
5V
–5V
ENABLE
LT6233
≈ 200V BIAS
ADVANCED PHOTONIX
012-70-62-541
WWW.ADVANCEDPHOTONIX.COM
OUTPUT OFFSET = 500µV TYPICAL
BANDWIDTH = 7.8MHz
OUTPUT NOISE = 1mV
P-P
(20MHz MEASUREMENT BW)
623345 TA02a
C1
2.7pF
100ns/DIV
623345 TA02b
50mV/DIV