OPA695 OPA 695 SBOS293G – DECEMBER 2003 – REVISED APRIL 2009 www.ti.com Ultra-Wideband, Current-Feedback OPERATIONAL AMPLIFIER With Disable FEATURES DESCRIPTION ● ● ● ● ● ● ● ● The OPA695 is a very high bandwidth, current-feedback op amp that combines an exceptional 4300V/µs slew rate and a low input voltage noise to deliver a precision, low-cost, high dynamic range Intermediate Frequency (IF) amplifier.
ABSOLUTE MAXIMUM RATINGS(1) ELECTROSTATIC DISCHARGE SENSITIVITY Power Supply ............................................................................... ±6.5VDC Internal Power Dissipation ..................................... See Thermal Analysis Differential Input Voltage .................................................................. ±1.2V Input Common-Mode Voltage Range ................................................. ±VS Storage Temperature Range: D, DBV ...........................
ELECTRICAL CHARACTERISTICS: VS = ±5V Boldface limits are tested at +25°C. RF = 402Ω, RL = 100Ω, and G = +8, (see Figure 1 for AC performance only), unless otherwise noted. OPA695ID, IDBV TYP CONDITIONS +25°C G = +1, RF = 523Ω G = +2, RF = 511Ω G = +8, RF = 402Ω G = +16, RF = 249Ω G = +2, VO = 0.5VPP, RF =523Ω RF = 523Ω, VO = 0.5VPP G = +8, VO = 4VPP G = –8, VO = 4V Step G = +8, VO = 4V Step G = +8, VO = 0.
ELECTRICAL CHARACTERISTICS: VS = +5V Boldface limits are tested at +25°C. RF = 348Ω, RL = 100Ω to VS /2, and G = +8, (see Figure 3 for AC performance only), unless otherwise noted. OPA695ID, IDBV TYP PARAMETER AC PERFORMANCE (see Figure 3) Small-Signal Bandwidth (VO = 0.5VPP) Bandwidth for 0.2dB Gain Flatness Peaking at a Gain of +1 Large-Signal Bandwidth Slew Rate Rise-and-Fall Time Settling Time to 0.02% 0.
TYPICAL CHARACTERISTICS: VS = ±5V G = +8, RF = 402Ω, RL = 100Ω, unless otherwise noted.
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) G = +8, RF = 402Ω, RL = 100Ω, unless otherwise noted. 10MHz HARMONIC DISTORTION vs LOAD RESISTANCE 10MHz HARMONIC DISTORTION vs SUPPLY VOLTAGE –50 –55 –60 –60 Harmonic Distortion (dBc) Harmonic Distortion (dBc) VO = 2VPP G = 8V/V 2nd-Harmonic –70 –80 3rd-Harmonic –90 VO = 2VPP, G = 8V/V RL = 100Ω 2nd-Harmonic –65 –70 –75 –80 3rd-Harmonic –85 –90 See Figure 1 See Figure 1 –100 –95 50 100 500 2.5 4.0 4.5 5.
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) G = +8, RF = 402Ω, RL = 100Ω, unless otherwise noted. TWO-TONE, 3rd-ORDER INTERMODULATION INTERCEPT ±5V INPUT VOLTAGE AND CURRENT NOISE DENSITY 100 45 Inverting 50Ω G = –8 Inverting Input Current Noise Noninverting Input Current Noise Output Intercept (+dBm) Current Noise (pA/√Hz) Voltage Noise (nV/√Hz) 40 22pA/√Hz 19pA/√Hz 10 1.7nV/√Hz Input Voltage Noise Noninverting 50Ω 402Ω 50Ω PI 35 G = 12dB to matched load.
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) G = +8, RF = 402Ω, RL = 100Ω, unless otherwise noted.
TYPICAL CHARACTERISTICS: VS = ±5V (Cont.) G = +8, RF = 402Ω, RL = 100Ω, unless otherwise noted.
TYPICAL CHARACTERISTICS: VS = ±5V Differential Operation GD = 10, RF = 500Ω, RL = 800Ω, unless otherwise noted. DIFFERENTIAL SMALL-SIGNAL FREQUENCY RESPONSE +5V 2 OPA695 0 RF 500Ω RG 1:1 VI Normalized Gain (dB) –5V ZI = RT || 2RG RT RL VO 800Ω RF 500Ω RG GD = 5 1 +5V VO 500Ω = = GD RG VI VO = 2VPP GD = 10 −1 −2 GD = 20 −3 −4 −5 −6 −7 OPA695 −8 1 10 –5V LARGE-SIGNAL BANDWIDTH 21.0 20.5 Harmonic Distortion (dBc) 20.0 Gain (dB) 19.5 VO = 8VPP 19.0 18.5 VO = 12VPP 17.
TYPICAL CHARACTERISTICS: VS = +5V VS = +5V, G = +8, RF = 348Ω, RL = 100Ω, unless otherwise noted. NONINVERTING SMALL-SIGNAL FREQUENCY RESPONSE INVERTING SMALL-SIGNAL FREQUENCY RESPONSE 6 6 G = +2, RF = 487Ω 0 –3 –6 –9 G = +8, RF = 348Ω –12 –15 –18 G = +16, RF = 162Ω –21 0 200 0 G = –4, RF = 442Ω –3 –6 –9 –12 G = –16, RF = 806Ω RG = 50Ω –15 See Figure 4 –24 400 600 800 1GHz 0 200 400 Frequency (200MHz/div) 100MHz, Square Wave Input 600 1GHz INVERTING PULSE RESPONSE 4.
TYPICAL CHARACTERISTICS: VS = +5V (Cont.) VS = +5V, G = +8, RF = 348Ω, RL = 100Ω, unless otherwise noted. 10MHz HARMONIC DISTORTION vs OUTPUT VOLTAGE HARMONIC DISTORTION vs FREQUENCY –55 Harmonic Distortion (dBc) –50 VO = 2VPP RL = 100Ω G = +8V/V G = +8V/V RL = 100Ω 2nd-Harmonic –55 Harmonic Distortion (dBc) –50 –60 3rd-Harmonic –65 –70 –75 –80 2nd-Harmonic –60 –65 –70 3rd-Harmonic –75 –80 –85 –85 See Figure 3 See Figure 3 –90 –90 0.5 Frequency (MHz) 1.0 1.
APPLICATIONS INFORMATION WIDEBAND CURRENT FEEDBACK OPERATION The OPA695 gives a new level of performance in wideband current feedback op amps. Nearly constant AC performance over a wide gain range, along with 4300V/µs slew rate, gives a lower power and cost solution for high-intercept IF amplifier requirements. While optimized at a gain of +8V/V (12dB to a matched 50Ω load) to give 450MHz bandwidth, applications from gains of 1 to 40 can be supported.
matched load). The circuit of Figure 3 shows a blocking capacitor driving into a 50Ω output resistor then into a 50Ω load. Alternatively, the blocking capacitor could be removed with the load tied to a supply midpoint or to ground if the DC current required by this grounded load is acceptable. Figure 3 shows the AC-coupled, single +5V supply, gain of +8V/V circuit configuration used as a basis for the +5V only Specifications and Typical Characteristic curves.
The single-supply test circuits of Figures 3 and 4 show +5V operation. These same circuits can be used over a singlesupply range of +5V to +12V. Operating on a single +12V supply, with the Absolute Maximum Supply voltage specification of +13V, gives adequate design margin for the typical ±5% supply tolerance. RF SPECIFICATIONS AND APPLICATIONS The ultra-high, full-power bandwidth and 3rd-order intercept of the OPA695 may be used to good advantage in IF amplifier applications.
curves. The inverting configuration holds almost constant bandwidth (with correctly selected external resistor values) until RG reduces to equal 50Ω, and remains at that value to satisfy the input impedance matching requirement, with further increases in gain achieved by increasing RF in Figure 2. The bandwidth then decreases rapidly as shown by the gain of –16V/V plot in the Typical Characteristic curves.
NOISE FIGURE All fixed-gain RF amplifiers show a very good noise figure (typically < 5dB). For broadband amplifiers, this is achieved by a low-noise input transistor and an input match set by feedback. This feedback greatly reduces the noise figure for fixed-gain RF amplifiers, but also makes the input match dependent on the load and the output match dependent on the source impedance at the input.
SAW FILTER BUFFER +12V 5kΩ 50Ω 1000pF 5kΩ OPA695 0.1µF PO Matching Network 50Ω 50Ω Source 1000pF SAW Filter 50Ω 400Ω PO PI PI = 12dB – (SAW Loss) FIGURE 6. IF Amplifier Driving SAW Filter. 50 Output Intercept (dBm) One common requirement in an IF strip is to buffer the output of a mixer with enough gain to recover the insertion loss of a narrowband SAW filter. Figure 6 shows one possible configuration driving a SAW filter. Figure 7 shows the intercept at the 50Ω load.
WIDEBAND CABLE DRIVING APPLICATIONS An alternative to this circuit, giving even lower distortion, is a differential driver using two OPA695s driving into an output transformer. This can be used either to double the available line power, or to improve distortion by cutting the required output swing in half for each stage. The channel disable required by the MCNS specification should be implemented by using the PGA disable feature.
tary output that is typically discarded into a matching resistor. The complementary current output can be used as an auxiliary output if it is inverted, as shown in Figure 11. bandwidth of 600MHz, which will then support up to 1.26GHz pixel rates. Figure 10 shows an example where three OPA695s provide an auxiliary monitor output for a highresolution RGB RAMDAC.
For a 20mA peak output current DAC, the mid-scale current of 10mA will give a 2V DC output common-mode operating voltage due to the 200Ω resistor to ground at the outputs. The total AC impedance at each output is 50Ω, giving a ±0.5V swing around this 2V common-mode voltage for the DAC. These resistors also act as a current divider, sending 75% of the DAC output current through the feedback resistor (464Ω).
DIFFERENTIAL I/O APPLICATIONS The OPA695 offers very low 3rd-order distortion terms with a dominant 2nd-order distortion for the single amplifier operation. For the lowest distortion, particularly where differential outputs are needed, operating two OPA695s in a differential I/O design will suppress these even-order terms, delivering extremely low harmonic distortion through high frequencies and powers.
noninverting inputs again have a gain of 1 to the output pins, giving particularly easy common-mode control for singlesupply operation. The OPA695 used in this configuration does constrain the feedback to the 500Ω region for best frequency response. With RF fixed, the input resistors may be adjusted to the desired gain, but will also be changing the input impedance as well. The high-frequency common-mode gain for this circuit from input to output will be the same as for the signal gain.
The buffer gain is typically very close to 1.00 and is normally neglected from signal gain considerations. It will, however, set the CMRR for a single op amp differential amplifier configuration. For the buffer gain α < 1.0, the CMRR = –20 • log (1 – α). RI, the buffer output impedance, is a critical portion of the bandwidth control equation. For the OPA695, it is typically about 28Ω for ±5V operation and 31Ω for single +5V operation.
Inverting feedback optimization is somewhat complicated by the impedance matching requirement at the input, as shown in Figure 2. The resistor values shown in Table III should be used in this case. OUTPUT CURRENT AND VOLTAGE The OPA695 provides output voltage and current capabilities that are consistent with driving doubly-terminated 50Ω lines. For a 100Ω load at a gain of +8 (see Figure 1), the total load is the parallel combination of the 100Ω load and the 456Ω total feedback network impedance.
The OPA695 has extremely low 3rd-order harmonic distortion. This also gives a high 2-tone, 3rd-order intermodulation intercept, as shown in the Typical Characteristic curves. This intercept curve is defined at the 50Ω load when driven through a 50Ω matching resistor to allow direct comparisons to RF MMIC devices and is shown for both gains of ±8. There is a slight improvement in intercept by operating the OPA695 in the inverting mode.
somewhat higher and are unmatched. Although bias current cancellation techniques are very effective with most voltagefeedback op amps, they do not generally reduce the output DC offset for wideband current-feedback op amps. Since the two input bias currents are unrelated in both magnitude and polarity, matching the source impedance looking out of each input to reduce their error contribution to the output is ineffective.
BOARD LAYOUT GUIDELINES point for design. Note that a 523Ω feedback resistor, rather than a direct short, is required for the unity gain follower application. A current-feedback op amp requires a feedback resistor—even in the unity gain follower configuration—to control stability. Achieving optimum performance with a high-frequency amplifier like the OPA695 requires careful attention to board layout parasitics and external component types.
INPUT AND ESD PROTECTION The OPA695 is built using a very high-speed, complementary bipolar process. The internal junction breakdown voltages are relatively low for these very small geometry devices. These breakdowns are reflected in the Absolute Maximum Ratings table where an absolute maximum ±6.5V supply is reported. All device pins have limited ESD protection using internal diodes to the power supplies, as shown in Figure 19.
Revision History DATE REVISION 4/09 G 7/06 F PAGE SECTION 1 Front Page 1, 4, 5 Various 2 Absolute Maximum Ratings DESCRIPTION Updated front page appearance. Added DGK (MSOP-8) package to Package Ordering Information table and to Thermal Resistance specification in the Electrical Characteristics tables. Changed Storage Temperature Range from −40°C to +125C to −65°C to +125C. NOTE: Page numbers for previous revisions may differ from page numbers in the current version. 30 OPA695 www.ti.
PACKAGE OPTION ADDENDUM www.ti.
PACKAGE OPTION ADDENDUM www.ti.com 18-Oct-2013 (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device.
PACKAGE MATERIALS INFORMATION www.ti.com 24-Jul-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ OPA695IDBVR SOT-23 3000 180.0 DBV 6 Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) 8.4 3.2 3.1 1.39 4.0 W Pin1 (mm) Quadrant 8.0 Q3 OPA695IDBVT SOT-23 DBV 6 250 180.0 8.4 3.2 3.1 1.39 4.0 8.0 Q3 OPA695IDGKR VSSOP DGK 8 2500 330.0 12.4 5.3 3.4 1.4 8.0 12.
PACKAGE MATERIALS INFORMATION www.ti.com 24-Jul-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) OPA695IDBVR SOT-23 DBV 6 3000 210.0 185.0 35.0 OPA695IDBVT SOT-23 DBV 6 250 210.0 185.0 35.0 OPA695IDGKR VSSOP DGK 8 2500 367.0 367.0 35.0 OPA695IDGKT VSSOP DGK 8 250 210.0 185.0 35.0 OPA695IDR SOIC D 8 2500 367.0 367.0 35.
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