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Wideband, Low-Noise, Voltage-Feedback

OPERATIONAL AMPLIFIER

APPLICATIONS

● HIGH DYNAMIC RANGE ADC PREAMPS

● LOW-NOISE, WIDEBAND, TRANSIMPEDANCE

AMPLIFIERS

● WIDEBAND, HIGH GAIN AMPLIFIERS

● LOW-NOISE DIFFERENTIAL RECEIVERS

● VDSL LINE RECEIVERS

● ULTRASOUND CHANNEL AMPLIFIERS

● SECURITY SENSOR FRONT ENDS

● UPGRADE FOR THE OPA686, CLC425, AND

LMH6624

FEATURES

● HIGH BANDWIDTH: 400MHz (G = +10)

● LOW INPUT VOLTAGE NOISE: 1.2nV/

√Hz

● VERY LOW DISTORTION: –100dBc (5MHz)

● HIGH SLEW RATE: 625V/µs

● HIGH DC ACCURACY: V

±150µV

● LOW SUPPLY CURRENT: 12.6mA

● HIGH GAIN BANDWIDTH PRODUCT: 1750MHz

● STABLE FOR GAINS

≥ 7

DESCRIPTION

The OPA846 combines very high gain bandwidth and large

signal performance with very low input voltage noise, while

dissipating a low 12.6mA supply current. The classical differ-

ential input stage, along with two stages of forward gain and

a high power output stage, combine to make the OPA846 an

exceptionally low distortion amplifier with excellent DC accu-

racy and output drive. The voltage-feedback architecture

allows all standard op amp applications to be implemented

with very high performance.

The combination of low input voltage and current noise,

along with a 1.75GHz gain bandwidth product, make the

OPA846 an ideal amplifier for wideband transimpedance

stages. As a voltage gain stage, the OPA846 is optimized for

a flat response at a gain of +10 and is stable down to a gain

of +7.

High Gain, 20MHz Transimpedance Amplifier

A new external compensation technique can be used to give

a very flat frequency response below the minimum stable

gain for the OPA846, further improving its already excep-

tional distortion performance. Using this compensation makes

the OPA846 one of the premier 12- to 16-bit Analog-to-Digital

(A/D) converter input drivers. The supply current for the

OPA846 is precisely trimmed to 12.6mA at +25°C. This,

along with carefully defined supply current tempco in the

input and output stages, combine to provide exceptional

performance over the full specified temperature range.

OPA846 RELATED PRODUCTS

INPUT NOISE GAIN BANDWIDTH

SINGLES VOLTAGE (nV/

√Hz

) PRODUCT (MHz)

OPA842 2.4 200

OPA843 2.0 800

OPA847 0.85 3900

OPA846

SBOS250E – JULY 2002 – REVISED DECEMBER 2008

www.ti.com

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

OPA846

+5V

–5V

50kΩ

0.1µF100pF

50kΩ

0.2pF

10pF

Photodiode

–V

Power-supply

decoupling not shown.

100

Frequency (MHz)

WIDEBAND TRANSIMPEDANCE

0.1 1 10 100

20 • log(Z

) [5dB/div]

20 log(50kΩ) = 94dBΩ

OPA846

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

All trademarks are the property of their respective owners.

Summary of content (29 pages)

PAGE 1
OPA OPA84 OPA846 846 6 www.ti.
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ABSOLUTE MAXIMUM RATINGS(1) ELECTROSTATIC DISCHARGE SENSITIVITY Power Supply ............................................................................... ±6.5VDC Internal Power Dissipation ........................ See Thermal Analysis Section Differential Input Voltage .................................................................. ±1.2V Input Voltage Range ............................................................................ ±VS Storage Temperature Range: D, DBV ...........................
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ELECTRICAL CHARACTERISTICS: VS = ±5V Boldface limits are tested at +25°C. RF = 453Ω, RL = 100Ω, and G = +10, unless otherwise noted. See Figure 1 for AC performance. OPA846ID, IDBV TYP PARAMETER AC PERFORMANCE (see Figure 1) Closed-Loop Bandwidth Gain Bandwidth Product (GBP) Bandwidth for 0.1dB Gain Flatness Peaking at a Gain of +7 Harmonic Distortion 2nd-Harmonic 3rd-Harmonic 2-Tone, 3rd-Order Intercept Input Voltage Noise Input Current Noise Rise-and-Fall Time Slew Rate Settling Time to 0.01% 0.
PAGE 4
TYPICAL CHARACTERISTICS: VS = ±5V TA = 25°C, G = +10, RF = 453Ω, RG = 50Ω, and RL = 100Ω, unless otherwise noted. NONINVERTING SMALL-SIGNAL FREQUENCY RESPONSE 6 VO = 0.2VPP INVERTING SMALL-SIGNAL FREQUENCY RESPONSE 3 G = +7 G = +10 G = –12 0 Normalized Gain (dB) 0 –3 –6 –9 G = +20 –12 –3 –12 –15 See Figure 1 See Figure 2 –18 –18 1 23 20 10 100 1000 1 INVERTING LARGE-SIGNAL FREQUENCY RESPONSE RL = 100Ω G = +10V/V 29 VO = 0.2VPP 26 VO = 1VPP 23 VO = 2VPP 14 11 VO = 0.
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TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = 25°C, G = +10, RF = 453Ω, RG = 50Ω, and RL = 100Ω, unless otherwise noted.
PAGE 6
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = 25°C, G = +10, RF = 453Ω, RG = 50Ω, and RL = 100Ω, unless otherwise noted. INPUT VOLTAGE AND CURRENT NOISE 2-TONE, 3RD-ORDER INTERMODULATION INTERCEPT 50 10 G = +10V/V 50Ω Source PIN Intercept Point (+dBm) Voltage Noise (nV/√Hz) Current Voise (pA/√Hz) 45 2.8pA/√Hz Current Noise 1.2nV/√Hz Voltage Noise –5V RF 453Ω 40 RG 50Ω 35 30 100 1k 10k 100k 1M 10M 100M 5 10 15 20 Frequency (Hz) 0.2 NG = 8.0 2 NG = 8.5 NG = 9.0 0.1 0 –0.
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TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = 25°C, G = +10, RF = 453Ω, RG = 50Ω, and RL = 100Ω, unless otherwise noted.
PAGE 8
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = 25°C, G = +10, RF = 453Ω, RG = 50Ω, and RL = 100Ω, unless otherwise noted. PHOTODIODE TRANSIMPEDANCE FREQUENCY RESPONSE SETTLING TIME 0.25 0.15 Transimpedance Gain (dBΩ) 0.10 0.05 0 –0.05 –0.10 –0.15 –0.20 RF = 10kΩ CF Adjusted 80 CD = 100pF 77 CD = 50pF 74 71 CD = 20pF 68 65 See Figure 1 See Figure 4 –0.25 62 0 5 10 15 20 1 25 10 SUPPLY AND OUTPUT CURRENT vs TEMPERATURE TYPICAL DC DRIFT OVER TEMPERATURE 0.25 15 0.10 10 VIO 0.
PAGE 9
TYPICAL CHARACTERISTICS: VS = ±5V TA = 25°C, GD = 20, RG = 50Ω, and RL = 400Ω, unless otherwise noted.
PAGE 10
APPLICATIONS INFORMATION WIDEBAND, NONINVERTING OPERATION The OPA846 provides a unique combination of features. Low input voltage noise, along with a very low distortion output stage, gives one of the highest dynamic range op amps available. The very high Gain Bandwidth Product (GBP) can be used either to deliver high signal bandwidths at high gain, or to deliver very low distortion signals at moderate frequencies and lower gains.
PAGE 11
WIDEBAND, HIGH-SENSITIVITY TRANSIMPEDANCE DESIGN The high GBP and low input voltage and current noise for the OPA846 make it an ideal wideband transimpedance amplifier. Very high transimpedance gains (> 100kΩ) benefit from the low input noise current of a JFET-input op amp, such as the OPA657. Unity-gain stability in the op amp is not required for application as a transimpedance amplifier. One transimpedance design example is shown on the front page of this data sheet.
PAGE 12
diode capacitance changes, the feedback capacitor must change to maintain a stable and flat frequency response. Using Equation 1, CF is adjusted to give the Butterworth frequency responses presented in Figure 4. +5V Power-supply decoupling not shown. 0.01µF PHOTODIODE TRANSIMPEDANCE FREQUENCY RESPONSE Tranimpedance Gain (dB Ω) 83 20 log(10kΩ) RF = 10kΩ CF Adjusted 80 OPA846 VO = – RF RG VI –5V CD = 10pF RG 250Ω 77 RF 500Ω VI 74 71 0.
PAGE 13
former primary as a 50Ω input matching impedance. The noninverting signal gain (noise gain, NG) to the amplifier output is then 1 + 1000/400 = 3.5V/V. Taking the input voltage noise (1.2nV/√Hz ) for the OPA846 times this noise gain to the output, then reflecting this noise term to the input side of the RG resistor, divides it by 5. This gives a net gain of 0.7 for the noninverting input voltage noise when reflected to the input point for the op amp circuit.
PAGE 14
result. However, operation at low gains may be desirable to take advantage of the higher slew rate and exceptional DC precision of the OPA846. Numerous external compensation techniques are suggested for operating a high-gain op amp at low gains. Most of these give zero/pole pairs in the closedloop response that cause long term settling tails in the pulse response and/or phase nonlinearity in the frequency response.
PAGE 15
possible noise contributors is required. Figure 13 shows the op amp noise analysis model with all the noise terms included. In this model, all the terms are taken to be noise voltage or current density terms in either nV/√Hz or pA/√Hz. +VCC +5V 2RF 0.01µF 2RF +12V Range Power-supply decoupling not shown. V R VO = CC – VI F OPA846 2 RG ENI RG EO OPA846 RS IBN RF VI ERS RF √4kTRS FIGURE 12. Single-Supply Inverting Amplifier. 4kT RG DESIGN-IN TOOLS IBI RG √4kTRF 4kT = 1.
PAGE 16
FREQUENCY RESPONSE CONTROL Voltage-feedback op amps exhibit decreasing closed-loop bandwidth as the signal gain is increased. In theory, this relationship is described by the GBP shown in the Electrical Characteristics. Ideally, dividing GBP by the noninverting signal gain (also called the noise gain, or NG) predicts the closed-loop bandwidth. In practice, this only holds true when the phase margin approaches 90°, as it does in high-gain configurations.
PAGE 17
DC ACCURACY AND OFFSET CONTROL The OPA846 can provide excellent DC signal accuracy due to its high open-loop gain, high common-mode rejection, high power-supply rejection, and low input offset voltage and bias current offset errors. To take full advantage of its low ±0.6mV maximum (25°C) input offset voltage, careful attention to input bias current cancellation is also required.
PAGE 18
BOARD LAYOUT +5V VCC Power-supply decoupling not shown. 48Ω 0.1µF OPA846 VO a) Minimize parasitic capacitance to any AC ground for all of the signal I/O pins. Parasitic capacitance on the output and inverting input pins can cause instability: on the noninverting input, it can react with the source impedance to cause unintentional bandlimiting. To reduce unwanted capacitance, create a window around the signal I/O pins leave opened in all of the ground and power planes around those pins.
PAGE 19
d) Connections to other wideband devices on the board may be made with short direct traces or through onboard transmission lines. For short connections, consider the trace and the input to the next device as a lumped capacitive load. Relatively wide traces (50mils to 100mils) should be used, preferably with ground and power planes opened up around them. Estimate the total capacitive load and set RS from the plot of Recommended RS vs Capacitive Load.
PAGE 20
Revision History DATE REVISION PAGE 12/08 E 2 3/06 D 15 SECTION DESCRIPTION Absolute Maximum Ratings Changed minimum Storage Temperature Range from −40°C to −65°C. Design-In Tools Board part number changed. NOTE: Page numbers for previous revisions may differ from page numbers in the current version. 20 OPA846 www.ti.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 (4) Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Top-Side Marking for that device. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided.
PAGE 23
PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) OPA846IDBVR SOT-23 DBV 5 3000 180.0 OPA846IDBVT SOT-23 DBV 5 250 OPA846IDR SOIC D 8 2500 B0 (mm) K0 (mm) P1 (mm) 8.4 3.2 3.1 1.39 4.0 180.0 8.4 3.2 3.1 1.39 330.0 12.4 6.4 5.2 2.1 Pack Materials-Page 1 W Pin1 (mm) Quadrant 8.0 Q3 4.0 8.0 Q3 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) OPA846IDBVR SOT-23 DBV 5 3000 210.0 185.0 35.0 OPA846IDBVT SOT-23 DBV 5 250 210.0 185.0 35.0 OPA846IDR SOIC D 8 2500 367.0 367.0 35.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.