LT1806/LT1807
28
18067fc
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2000
LT 0809 REV C • PRINTED IN USA
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1395 400MHz Current Feedback Amplifi er 800V/μs Slew Rate, Shutdown
LT1399 Triple 300MHz Current Feedback Amplifi er 0.1dB Gain Flatness to 150MHz, Shutdown
LT1632/LT1633 Dual/Quad 45MHz, 45V/μs Rail-to-Rail Input and Output Amplifi ers High DC Accuracy 1.35mV V
OS(MAX)
, 70mA Output Current,
Max Supply Current 5.2mA/Amp
LT1809/LT1810 Single/Dual 180MHz Input and Output Rail-to-Rail Amplifi ers 350V/μs Slew Rate, Shutdown, Low Distortion –90dBc at 5MHz
LT1812/LT1813 3mA, 100MHz, 750V/μs Op Amp High Slew Rate
LT1818/LT1819 9mA, 400MHz, 2500V/μs Op Amp Ultrahigh Slew Rate
LT6200/LT6201 165MHz Rail-to-Rail Input and Output, 0.95nV/√Hz Low Noise
Op Amp
Lowest Noise
LT6202/LT6203 100MHz Rail-to-Rail Input and Output, 1.9nV/√Hz Op Amp I
CC
= 2.5mA
TYPICAL APPLICATION
FET Input, Fast, High Gain Photodiode Amplifi er
Figure 10 shows a fast, high gain transimpedance
amplifi er applied to a photodiode. A JFET buffer is used
for its extremely low input bias current and high speed.
The LT1097 and 2N3904 keep the JFET biased at I
DSS
for zero offset and lowest voltage noise. The JFET then
drives the LT1806, with R
F
closing the high speed loop
back to the JFET input and setting the transimpedance
gain. C4 helps improve the phase margin of the fast loop.
Output voltage noise density was measured as 9nV/√Hz
with R
F
short circuited. With R
F
varied from 100k to 1M,
total output noise was below 1mV
RMS
measured over a
10MHz bandwidth. Table 4 shows results achieved with
various values of R
F
and Figure 11 shows the time domain
response with R
F
= 499k.
Table 4. Results Achieved for Various R
F
, 1.2V Output Step
R
F
10% to 90%
RISE TIME
–3dB
BANDWIDTH
100k 64ns 6.8MHz
200k 94ns 4.6MHz
499k 154ns 3MHz
1M 263ns 1.8MHz
Figure 10. Fast, High Gain Photodiode Amplifi er
–
+
R3
10k
R1
10M
SIEMENS/
INFINEON
SFH213FA
PHOTODIODE
R2
1M
R
F
49.9Ω
50W
18067 F10
R5
33Ω
R4
2.4k
3
6
4
7
V
S
+
V
S
–
V
S
–
2
C2
2200pF
C3
0.1μF
C1
100pF
C4
3pF
LT1097
–
+
2
6
4
7
V
OUT
*
2N5486
V
S
+
V
S
+
V
S
–
V
S
–
3
LT1806
2N3904
*ADJUST PARASITIC CAPACITANCE AT
R
F
FOR DESIRED RESPONSE
CHARACTERISTICS
V
S
= p5V
Figure 11. Step Response
with R
F
= 499k
20ns/DIV
100mV/DIV
18067 F11
