LT1801 LINER [Linear Technology], LT1801 Datasheet - Page 20

• Manufacturer Part Number: LT1801
• Description: Dual/Quad 80MHz, 25V/?s Low Power Rail-to-Rail Input and Output Precision Op Amps
• Manufacturer: LINER [Linear Technology]

TYPICAL APPLICATIO
Low Power High Voltage Amplifier
Certain materials used in optical applications have charac-
teristics that change due to the presence and strength of
a DC electric field. The voltage applied across these
materials should be precisely controlled to maintain de-
sired properties, sometimes as high as 100’s of volts. The
materials are not conductive and represent a capacitive
load.
The circuit of Figure 6 shows the LT1801 used in an
amplifier capable of a 250V output swing and providing
LT1801/LT1802
RELATED PARTS
20
PART NUMBER
LT1399
LT1498/LT1499 Dual/Quad 10MHz, 6V/µs Rail-to-Rail Input and Output C-Load
LT1630/LT1631 Dual/Quad 30MHz, 10V/µs Rail-to-Rail Input and Output Op Amps
LT1800
LT1806/LT1807 Single/Dual 325MHz, 140V/µs Rail-to-Rail Input and Output Op Amps
LT1809/LT1810 Single/Dual 180MHz Rail-to-Rail Input/Output Op Amps
C-Load is a trademark of Linear Technology Corporation.
V
IN
150V
8pF
C2
0.1µF
R2
2k
R1
2k
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone]
R3
200k
+
–
1/2 LT1801
DESCRIPTION
Triple 300MHz Current Feedback Amplifier
80MHz, 25V/µs Low Power Rail-to-Rail Input/Output Precision Op Amp
Figure 6. Low Power, High Voltage Amplifier
39pF
5V
C1
●
FAX: [phone]
Q1
Q3
5V
10k
10k
R4
R5
2k
2k
Q5
Q7
Q2
Q4
4.99k
4.99k
–130V
U
130V
5V
R6
2k
R7
2k
Q6
●
Q8
18012 F06
1k
1k
www.linear.com
A
±130V SUPPLY I
OUTPUT SWING = ±128.8V
OUTPUT OFFSET ≅ 20mV
OUTPUT SHORT-CIRCUIT CURRENT ≅ 3mA
10% TO 90% RISE TIME ≅ 8µs, 200V OUTPUT STEP
SMALL-SIGNAL BANDWIDTH ≅ 150kHz
Q1, Q2, Q7, Q8: ON SEMI MPSA42
Q3, Q4, Q5, Q6: ON SEMI MPSA92
V
V
OUT
= V
MATERIAL UNDER
ELECTRIC FIELD
100pF
OUT
/V
IN
= –100
Q
= 130µA
precise DC output voltage. When no signal is present, the
op amp output sits at about mid-supply. Transistors Q1
and Q3 create bias voltages for Q2 and Q4, which are
forced into a low quiescent current by degeneration resis-
tors R4 and R5. When a transient signal arrives at V
op amp output moves and causes the current in Q2 or Q4
to change depending on the signal polarity. The current,
limited by the clipping of the LT1801 output and the 3kΩ
of total emitter degeneration, is mirrored to the output
devices to drive the capacitive load. The LT1801 output
then returns to near mid-supply, providing the precise DC
output voltage to the load. The attention to limit the current
of the output devices minimizes power dissipation thus
allowing for dense layout, and inherits better reliability.
Figure 7 shows the time domain response of the amplifier
providing a 200V output swing into a 100pF load.
TM
Op Amps High DC Accuracy, 475µV V
COMMENTS
0.1dB Gain Flatness to 150MHz, Shutdown
High DC Accuracy, 525µV V
Max Supply Current 4.4mA per Amplifier
Single Version of LT1801/LT1802
High DC Accuracy, 550µV V
Low Distortion –80dB at 5MHz, Power-Down (LT1806)
350V/µs Slew Rate, Low Distortion –90dBc at 5MHz,
Power-Down (LT1809)
50V/DIV
2V/DIV
V
OUT
V
IN
Figure 7. Large-Signal Time Domain
Response of the Amplifier
© LINEAR TECHNOLOGY CORPORATION 2002
OS(MAX)
OS(MAX)
OS(MAX)
LT 0607 REV B • PRINTED IN USA
10µs/DIV
, 4µV/°C Max Drift
, 70mA Output Current,
, Low Noise 3.5nV/√Hz,
IN
18012fb
, the
18012 F07