LT1802CS datasheet(20/20 Pages) LINER

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LT1801/LT1802

18012fb

LT 0607 REV B • PRINTED IN USA

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

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

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 VIN, the

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 3k

Ω

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.

PART NUMBER

DESCRIPTION

COMMENTS

LT1399

Triple 300MHz Current Feedback Amplifier

0.1dB Gain Flatness to 150MHz, Shutdown

LT1498/LT1499

Dual/Quad 10MHz, 6V/

µs Rail-to-Rail Input and Output C-LoadTM Op Amps High DC Accuracy, 475µV VOS(MAX), 4µV/°C Max Drift

LT1630/LT1631

Dual/Quad 30MHz, 10V/

µs Rail-to-Rail Input and Output Op Amps

High DC Accuracy, 525

µV VOS(MAX), 70mA Output Current,

Max Supply Current 4.4mA per Amplifier

LT1800

80MHz, 25V/

µs Low Power Rail-to-Rail Input/Output Precision Op Amp

Single Version of LT1801/LT1802

LT1806/LT1807

Single/Dual 325MHz, 140V/

µs Rail-to-Rail Input and Output Op Amps

High DC Accuracy, 550

µV VOS(MAX), Low Noise 3.5nV/√Hz,

Low Distortion –80dB at 5MHz, Power-Down (LT1806)

LT1809/LT1810

Single/Dual 180MHz Rail-to-Rail Input/Output Op Amps

350V/

µs Slew Rate, Low Distortion –90dBc at 5MHz,

Power-Down (LT1809)

C-Load is a trademark of Linear Technology Corporation.

RELATED PARTS

TYPICAL APPLICATIO

1/2 LT1801

10k

4.99k

–130V

18012 F06

4.99k

200k

0.1

µF

39pF

8pF

150V

VOUT

VIN

MATERIAL UNDER

ELECTRIC FIELD

100pF

130V

AV = VOUT/VIN = –100

±130V SUPPLY IQ = 130µA

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

Figure 6. Low Power, High Voltage Amplifier

Figure 7. Large-Signal Time Domain

Response of the Amplifier

VIN

2V/DIV

VOUT

50V/DIV

µs/DIV

18012 F07

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