Photodiode Capacitance, CD (pF)

0

2

4

6

8

10

12

14

16

18

20

5

10

100

D100

RF = 20 k:

RF = 50 k:

RF = 100 k:

RF = 500 k:

OPA818

THS4541

V

REF1

V

BIAS

V

REF2

+

±

100 k

ADC

C

F

R

G1

R

G2

R

F1

R

F2

+

±

V

CM

+5 V

5 V

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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

OPA818

SBOS940A – MAY 2019 – REVISED MARCH 2020

OPA818 2.7-GHz, High-Voltage, FET-Input, Low Noise, Operational Amplifier

1

1 Features

1

•

High speed:

–

Gain-bandwidth product: 2.7 GHz

–

Bandwidth (G = 7 V/V): 765 MHz

–

Large-signal bandwidth (2 VPP): 400 MHz

–

Slew rate: 1400 V/µs

•

Decompensated gain: 7-V/V stable

•

Low noise:

–

Input voltage noise: 2.2 nV/

√Hz

–

Input current noise: 3 fA/

√Hz (f = 10 kHz)

•

Input bias current: 4 pA (typical)

•

Low input capacitance:

–

Common-mode: 1.9 pF

–

Differential mode: 0.5 pF

•

Low distortion (G = 7 V/V, RL = 1 kΩ, VO = 2 VPP):

–

HD2, HD3 at 1 MHz: –104 dBc, –108 dBc

–

HD2, HD3 at 50 MHz: –57 dBc, –72 dBc

•

Wide supply range: 6 V to 13 V

•

Output swing: 8 VPP (VS = 10 V)

•

Supply current: 27.7 mA

•

Shutdown supply current: 27 µA

•

Performance upgrade to OPA657

2 Applications

•

Wideband transimpedance amplifiers (TIAs)

•

Wafer scanning equipment

•

Optical communication modules

•

High-speed data acquisition (DAQ)

•

Active probes

•

Optical time-domain reflectometry (OTDR)

•

Test and measurement front-ends

•

Medical and chemical analyzers

High-Speed Optical Front-End

3 Description

The OPA818 is a decompensated, voltage-feedback

operational

amplifier

for

high-speed

and

wide

dynamic range applications. OPA818 has a low-noise

junction gate field-effect transistor (JFET) input stage

that combines high gain-bandwidth with a wide supply

range from 6 V to 13 V. The fast slew rate of

1400 V/µs provides high large-signal bandwidth and

low distortion. This amplifier is manufactured using

Texas Instruments' proprietary, high-speed, silicon-

germanium (SiGe) process to achieve significant

performance improvements over other high-speed,

FET-input amplifiers.

The OPA818 is an extremely versatile, wideband TIA

photodiode amplifier for use in optical test and

communication

equipment,

and

many

medical,

scientific, and industrial instruments. The OPA818

showcases 2.7 GHz gain-bandwidth, low 2.4 pF total

input capacitance, and 2.2 nV/

√Hz input noise. The

OPA818 can achieve over 85-MHz signal bandwidth

in TIA configuration with 20-kΩ TIA gain (RF) and

0.5-pF photodiode capacitance (CD) with wide output

swings. The decompensated, low-noise architecture

with pico amperes of input bias current is also well-

suited

for

high-gain

test

and

measurement

applications. Though normally stable in gains

≥ 7 V/V,

the OPA818 can be used in applications with lower

gains by applying noise-gain shaping techniques (see

Non-Inverting Gain of 2 V/V).

The OPA818 is available in an 8-lead WSON

package with an exposed thermal pad for heat

dissipation. This device is specified to operate over

the industrial temperature range of –40°C to +85°C.

Device Information(1)

PART NUMBER

PACKAGE

BODY SIZE (NOM)

OPA818

WSON (8)

3.00 mm × 3.00 mm

(1) For all available packages, see the package option addendum

at the end of the data sheet.

Photodiode Capacitance vs 3-dB Bandwidth