Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsLinear IC - Op-amp Voltage feedback SOIC 8

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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.

698

Unity-Gain Stable, Wideband

Voltage Limiting Amplifier

FEATURES

● HIGH LINEARITY NEAR LIMITING

● FAST RECOVERY FROM OVERDRIVE: 1ns

● LIMITING VOLTAGE ACCURACY: ±10mV

● –3dB BANDWIDTH (G = +1): 450MHz

● GAIN BANDWIDTH PRODUCT: 250MHz

● SLEW RATE: 1100V/µs

● ±5V AND +5V SUPPLY OPERATION

● HIGH-GAIN VERSION AVAILABLE: OPA699

APPLICATIONS

● FAST LIMITING ANALOG-TO-DIGITAL

CONVERTER (ADC) INPUT BUFFERS

● CCD PIXEL CLOCK STRIPPING

● VIDEO SYNC STRIPPING

● HF MIXERS

● IF LIMITING AMPLIFIERS

● AM SIGNAL GENERATION

●

NONLINEAR ANALOG SIGNAL PROCESSING

●

OPA688 UPGRADE

DESCRIPTION

The OPA698 is a wideband, unity-gain stable voltage-

feedback op amp that offers bipolar output voltage limiting.

Two buffered limiting voltages take control of the output

when it attempts to drive beyond these limits. This new

output limiting architecture holds the limiter offset error to

±10mV. The op amp operates linearly to within 20mV of the

output limit voltages.

The combination of a narrow nonlinear range and the low

limiting offset allows the limiting voltages to be set within

100mV of the desired linear output range. A fast 1ns

recovery from limiting ensures that overdrive signals will be

transparent to the signal channel. Implementing the limiting

function at the output, as opposed to the input, gives the

specified limiting accuracy for any gain, and allows the

OPA698 to be used in all standard op amp applications.

Nonlinear analog signal processing will benefit from the

ability of the OPA698 to sharply transition from linear opera-

tion to output limiting. The quick recovery time supports

high-speed applications.

The OPA698 is available in an industry standard pinout SO-8

package. For higher gain, or transimpedance applications

requiring output limiting with fast recovery, consider the

OPA699.

OPA698

SBOS258D – NOVEMBER 2002 – REVISED DECEMBER 2008

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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.

All trademarks are the property of their respective owners.

OPA698

= +5V

+3.5V

+1.5V

REFB

REFT

0.1µF

100pF

= +3.6V

= +1.4V

0.1µF

402Ω

24.9Ω

562Ω

102Ω

402Ω

715Ω

102Ω

562Ω

ADS822

10-Bit

40MSPS

10-Bit

Data

= +5V

INT/EXT

RSEL +V

GND

Single-Supply Limiting ADC Input Driver

Summary of content (32 pages)

PAGE 1
OPA698 OPA 698 SBOS258D – NOVEMBER 2002 – REVISED DECEMBER 2008 www.ti.
PAGE 2
ELECTROSTATIC DISCHARGE SENSITIVITY ABSOLUTE MAXIMUM RATINGS(1) Supply Voltage ............................................................................. ±6.5VDC Internal Power Dissipation .......................... See Thermal Characteristics Common-Mode Input Voltage ............................................................. ±VS Differential Input Voltage ..................................................................... ±VS Limiter Voltage Range .................................................
PAGE 3
ELECTRICAL CHARACTERISTICS: VS = ±5V Boldface limits are tested at +25°C. G = +2, RF = 402Ω, RL = 500Ω, and VH = –VL = 2V (see Figure 1 for AC performance only), unless otherwise noted. OPA698ID TYP PARAMETER AC PERFORMANCE (see Figure 1) Small-Signal Bandwidth Gain-Bandwidth Product (G ≥ +5) Gain Peaking 0.1dB Gain Flatness Bandwidth Large-Signal Bandwidth Step Response: Slew Rate Rise-and-Fall Time Settling Time: 0.
PAGE 4
ELECTRICAL CHARACTERISTICS: VS = ±5V (Cont.) Boldface limits are tested at +25°C. G = +2, RF = 402Ω, RL = 500Ω, and VH = –VL = 2V (see Figure 1 for AC performance only), unless otherwise noted. OPA698ID TYP CONDITIONS +25°C +25°C(1) 0°C to +70°C(2) –40°C to +85°C(2) 2x Overdrive VIN = 0 to ±2V Step VIN = ±2V to 0V Step f = 5MHz, VO = 2VPP 250 1 30 1.9 2 2.1 PARAMETER OUTPUT VOLTAGE LIMITERS (Cont.
PAGE 5
ELECTRICAL CHARACTERISTICS: VS = +5V Boldface limits are tested at +25°C. G = +2, RL = 500Ω tied to VCM = 2.5V, RF = 402Ω, VL = VCM –1.2V, and VH = VCM +1.2V (see Figure 2 for AC performance only), unless otherwise noted. OPA698ID TYP PARAMETER AC PERFORMANCE (see Figure 2) Small-Signal Bandwidth Gain-Bandwidth Product (G ≥ +5) Gain Peaking 0.1dB Gain Flatness Bandwidth Large-Signal Bandwidth Step Response: Slew Rate Rise-and-Fall Time Settling Time: 0.
PAGE 6
ELECTRICAL CHARACTERISTICS: VS = +5V (Cont.) Boldface limits are tested at +25°C. G = +2, RL = 500Ω tied to VCM = 2.5V, RF = 402Ω, VL = VCM –1.2V, and VH = VCM +1.2V (see Figure 2 for AC performance only), unless otherwise noted. OPA698ID TYP THERMAL CHARACTERISTICS Temperature Range Thermal Resistance D SO-8 –40°C to +85°C(2) MIN/ TEST MAX LEVEL(3) +25°C 2x Overdrive VIN = VCM to VCM ± 1.2V Step VIN = VCM ± 1.
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TYPICAL CHARACTERISTICS: VS = ±5V TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω, VH = –VL = 2V, unless otherwise noted. NONINVERTING SMALL-SIGNAL FREQUENCY RESPONSE 6 0 –3 VIN VO OPA698 RC –6 RF –9 VO = 0.
PAGE 8
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω, VH = –VL = 2V, unless otherwise noted. LARGE-SIGNAL PULSE RESPONSE SMALL-SIGNAL PULSE RESPONSE 0.25 VO = 0.2VPP 0.15 1.5 0.10 1.0 0.05 0.5 0.00 –0.05 0 –0.5 –0.10 –1.0 –0.15 –1.5 –0.20 VO = 4VPP VH = –VL = 2.5V 2.0 VOUT (V) VOUT (V) 0.20 2.5 –2.0 See Figure 1 See Figure 1 –2.5 –0.25 Time (5ns/div) Time (5ns/div) VH—LIMITED PULSE RESPONSE 2.5 2.0 2.0 1.5 1.5 VOUT 0.5 VIN 0 –0.5 –1.
PAGE 9
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω, VH = –VL = 2V, unless otherwise noted. 5MHz HARMONIC DISTORTION vs LOAD RESISTANCE 5MHz HARMONIC DISTORTION vs SUPPLY VOLTAGE –55 –45 VO = 2VPP f = 5MHz VO = 2VPP RL = 500Ω –50 Harmonic Distortion (dBc) Harmonic Distortion (dBc) –60 2nd-Harmonic –65 –70 –75 3rd-Harmonic –80 –85 –55 –60 2nd-Harmonic –65 –70 –75 3rd-Harmonic –80 –85 See Figure 1 –90 See Figure 1 –90 1k 100 2.5 3.0 3.
PAGE 10
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω, VH = –VL = 2V, unless otherwise noted. 2-TONE, 3RD-ORDER INTERMODULATION INTERCEPT ±5V 500Ω HARMONIC DISTORTION NEAR LIMITING VOLTAGES 50 VO = 0VDC ± 1VP f = 5MHz RL = 500Ω –50 G = +2V/V 45 Intercept Point (dBm) Harmonic Distortion (dBc) –40 –60 2nd-Harmonic –70 –80 40 PI 35 PO 50Ω OPA698 30 500Ω 402Ω 25 402Ω 3rd-Harmonic –90 20 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.
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TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω, VH = –VL = 2V, unless otherwise noted. VOLTAGE RANGE vs TEMPERATURE LIMITED VOLTAGE RANGE vs TEMPERATURE 5.0 3.8 VH = –VL = 4.3V VH and VL left open 4.5 ± Voltage Range (V) Output Voltage Range 4.0 3.5 3.6 3.5 VH 3.4 3.3 Common-Mode Input Range VL 3.0 3.
PAGE 12
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω, VH = –VL = 2V, unless otherwise noted. LIMITER FEEDTHROUGH CLOSED-LOOP OUTPUT IMPEDANCE –45 100 –50 10 Output Impedance (Ω) Feedthrough (dB) –55 –60 –65 0.02VPP + 2VDC –70 VH VO –75 OPA698 –80 VL 402Ω –85 G = +1 RF = 25Ω VO = 0.2VPP 1 0.1 0.01 402Ω Open –90 –95 0.
PAGE 13
TYPICAL CHARACTERISTICS: VS = +5V TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω to VCM = +2.5V, VL = VCM – 1.2V, VH = VCM + 1.2V, unless otherwise noted. INVERTING SMALL-SIGNAL FREQUENCY RESPONSE NONINVERTING SMALL-SIGNAL FREQUENCY RESPONSE 9 VO = 0.2VPP 6 Normalized Gain (dB) 0 0 –3 G = +2, RC = ∞ –6 G = –1 VO = 0.
PAGE 14
TYPICAL CHARACTERISTICS: VS = +5V TA = +25°C, G = +2, RF = 402Ω, and RL = 500Ω to VCM = +2.5V, VL = VCM – 1.2V, VH = VCM + 1.2V, unless otherwise noted. HARMONIC DISTORTION vs FREQUENCY HARMONIC DISTORTION vs LOAD RESISTANCE –50 –45 VO = 2VPP f = 5MHz –55 VO = 2VPP RL = 500Ω –55 Harmonic Distortion (dBc) Harmonic Distortion (dBc) –50 2nd-Harmonic –60 –65 3rd-Harmonic –70 –60 –65 2nd-Harmonic –70 –75 –80 3rd-Harmonic –75 –85 See Figure 2 See Figure 2 –90 –80 1k 100 0.
PAGE 15
TYPICAL APPLICATIONS WIDEBAND VOLTAGE LIMITING OPERATION The OPA698 is a voltage feedback amplifier that combines features of a wideband, high slew rate amplifier with output voltage limiters. Its output can swing up to 1V from each rail and can deliver up to 120mA. These capabilities make it an ideal interface to drive ADC while adding overdrive protection for the ADC inputs.
PAGE 16
WIDEBAND INVERTING OPERATION As the required RG resistor approaches 50Ω at higher gains, the bandwidth for the circuit in Figure 3 will far exceed the bandwidth at that same gain magnitude for the noninverting circuit of Figure 1. This occurs due to the lower noise gain for the circuit of Figure 3 when the 50Ω source impedance is included in the analysis.
PAGE 17
The gain for the circuit in Figure 5 is set at +2. Figure 8 shows a 100MHz sinewave amplifier, with a gain of +2 and rectified. LIMITED OUTPUT, DIFFERENTIAL ADC INPUT DRIVER Figure 6 shows a differential ADC driver that takes advantage of the OPA698 limiters to protect the input of the ADC. Two OPA698s are used. The first one is an inverting configuration at a gain of –2. The second one is in a noninverting configuration at a gain of +2.
PAGE 18
High-Speed Full Wave rectifier #1 The circuit shown in Figure 9 uses only one amplifier, in an inverting gain of –1 configuration. The upper limiting voltage is left open, resulting in an upper limiting voltage of +3.5V. The lower limiting voltage is connected to the input signal, resulting in the following behavior. When the input voltage is negative, the amplifier is not limiting, resulting in the inversion of the input sinewave to the output.
PAGE 19
R2 402Ω R1 1kΩ VCH +1V R1 200Ω R3 200Ω VH OPA698 R3 1kΩ R4 2kΩ VOUT VL VIN VIN VCL –1V +2V VREF R2 2kΩ –2V V OPA698 VHL VOUT FIGURE 15. Very High-Speed Schmitt Trigger. Figure 16 shows the Schmitt Trigger operating with VREF = +5V. This gives us VHH = 2.4V and VHL = 1.6V. The propagation delay for the OPA698 in a Schmitt Trigger configuration is 6ns from high-to-low, and 5ns from low-to-high. 24.9Ω FIGURE 13. Soft-Clipping Circuit.
PAGE 20
DESIGN-IN TOOLS DC RESTORER Figure 18 shows a DC restore circuit using the OPA698 and OPA660. The buffer element of the OPA660 is used to buffer the input signal while the transconductance element is used to restore the DC level after the decoupling capacitor C1. The DC level is set using R1 and R2. The OPA698 is configured at a gain of 2 to compensate for the 75Ω series into a 75Ω load. The OPA698 also limits the output to ground.
PAGE 21
OUTPUT LIMITERS The output voltage is linearly dependent on the input(s) when it is between the limiter voltages VH (pin 8) and VL (pin 5). When the output tries to exceed VH or VL, the corresponding limiter buffer takes control of the output voltage and holds it at VH or VL. Because the limiters act on the output, their accuracy does not change with gain.
PAGE 22
THERMAL CONSIDERATIONS The OPA698 will not require heat sinking under most operating conditions. Maximum desired junction temperature will set a maximum allowed internal power dissipation as described below. In no case should the maximum junction temperature be allowed to exceed 150°C. The total internal power dissipation (PD) is the sum of quiescent power (PDQ) and the additional power dissipated in the output stage (PDL) while delivering load power.
PAGE 23
2nd- and 3rd-Harmonic Distortion (dBc) The total output spot noise voltage can be computed as the square root of the sum of all squared output noise voltage contributors. Equation 3 shows the general form for the output noise voltage using the terms shown in Figure 25.
PAGE 24
A fine-scale output offset null, or DC operating point adjustment, is often required. Numerous techniques are available for introducing DC offset control into an op amp circuit. Most of these techniques eventually reduce to adding a DC current through the feedback resistor. In selecting an offset trim method, one key consideration is the impact on the desired signal path frequency response.
PAGE 25
g) When long traces are necessary, use transmission line design techniques (consult an ECL design handbook for microstrip and stripline layout techniques). A 50Ω transmission line is not required on board—a higher characteristic impedance will help reduce output loading. Use a matching series resistor at the output of the op amp to drive a transmission line, and a matched load resistor at the other end to make the line appear as a resistor.
PAGE 26
Revision History DATE REVISION PAGE 12/08 D 2 3/06 C 20 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. 26 OPA698 www.ti.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device OPA698IDR Package Package Pins Type Drawing SOIC D 8 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 12.4 Pack Materials-Page 1 6.4 B0 (mm) K0 (mm) P1 (mm) 5.2 2.1 8.0 W Pin1 (mm) Quadrant 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) OPA698IDR 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 JESD46C and to discontinue any product or service per JESD48B. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.