Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsLinear IC - Op-amp Variable gain SOIC 8

VCA810

+5V

-5V

OUT

0 2V® -

- ®40dB +40dB Gain

VCA810

V+

V-

Gain

Adjust

VCA810

www.ti.com

SBOS275F –JUNE 2003–REVISED DECEMBER 2010

High Gain Adjust Range, Wideband,

VARIABLE GAIN AMPLIFIER

Check for Samples: VCA810

Operating from ±5V supplies, the gain control voltage

FEATURES

for the VCA810 will adjust the gain from –40dB at 0V

• HIGH GAIN ADJUST RANGE: ±40dB

input to +40dB at –2V input. Increasing the control

• DIFFERENTIAL IN/SINGLE-ENDED OUT

voltage above ground will attenuate the signal path to

greater than 80dB. Signal bandwidth and slew rate

• LOW INPUT NOISE VOLTAGE: 2.4nV/√Hz

remain constant over the entire gain adjust range.

• CONSTANT BANDWIDTH vs GAIN: 35MHz

This 40dB/V gain control is accurate within ±1.5dB

• HIGH dB/V GAIN LINEARITY: ±0.3dB

(±0.9dB for high grade), allowing the gain control

• GAIN CONTROL BANDWIDTH: 25MHz

voltage in an AGC application to be used as a

Received Signal Strength Indicator (RSSI) with

• LOW OUTPUT DC ERROR: < ±40mV

±1.5dB accuracy.

• HIGH OUTPUT CURRENT: ±60mA

Excellent common-mode rejection and

• LOW SUPPLY CURRENT: 24.8mA

common-mode input range at the two

(max for −40°C to +85°C temperature range)

high-impedance inputs allow the VCA810 to provide a

differential receiver operation with gain adjust. The

APPLICATIONS

output signal is referenced to ground. Zero differential

• OPTICAL RECEIVER TIME GAIN CONTROL

input voltage gives a 0V output with a small dc offset

error. Low input noise voltage ensures good output

• SONAR SYSTEMS

SNR at the highest gain settings.

• VOLTAGE-TUNABLE ACTIVE FILTERS

• LOG AMPLIFIERS

In applications where pulse edge information is

critical, and the VCA810 is being used to equalize

• PULSE AMPLITUDE COMPENSATION

varying channel loss, minimal change in group delay

• AGC RECEIVERS WITH RSSI

over gain setting will retain excellent pulse edge

• IMPROVED REPLACEMENT FOR VCA610

information.

An improved output stage provides adequate output

current to drive the most demanding loads. While

principally intended to drive analog-to-digital

converters (ADCs) or second-stage amplifiers, the

±60mA output current will easily drive

doubly-terminated 50Ω lines or a passive post-filter

stage over the ±1.7V output voltage range.

VCA810 RELATED PRODUCTS

GAIN

ADJUST INPUT SIGNAL

RANGE NOISE BANDWIDTH

SINGLES DUALS (dB) (nV/√Hz) (MHz)

VCA811 — 80 2.4 80

— VCA2612 45 1.25 80

— VCA2613 45 1 80

— VCA2614 45 3.6 40

DESCRIPTION

— VCA2616 45 3.3 40

The VCA810 is a dc-coupled, wideband, continuously

VCA2618 45 5.5 30

variable, voltage-controlled gain amplifier. It provides

a differential input to single-ended output conversion

with a high-impedance gain control input used to vary

the gain over a –40dB to +40dB range linear in dB/V.

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.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (30 pages)

PAGE 1
VCA VCA810 810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 High Gain Adjust Range, Wideband, VARIABLE GAIN AMPLIFIER Check for Samples: VCA810 FEATURES Operating from ±5V supplies, the gain control voltage for the VCA810 will adjust the gain from –40dB at 0V input to +40dB at –2V input. Increasing the control voltage above ground will attenuate the signal path to greater than 80dB. Signal bandwidth and slew rate remain constant over the entire gain adjust range.
PAGE 2
VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 ELECTRICAL CHARACTERISTICS: VS = ±5V Boldface limits are tested at +25°C. At RL = 500Ω, and VIN = single-ended input on V+ with V− at ground,, unless otherwise noted.
PAGE 4
VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com ELECTRICAL CHARACTERISTICS: VS = ±5V (continued) Boldface limits are tested at +25°C. At RL = 500Ω, and VIN = single-ended input on V+ with V− at ground,, unless otherwise noted.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 HIGH GRADE DC SPECIFICATIONS: VS = ±5V (VCA810AID) Boldface limits are tested at +25°C. At RL = 500Ω, and VIN = single-ended input on V+ with V− at ground,, unless otherwise noted.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: VS = ±5V At RL = 500Ω and VIN = single-ended input on V+ with V− at ground, unless otherwise noted.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 TYPICAL CHARACTERISTICS: VS = ±5V (continued) At RL = 500Ω and VIN = single-ended input on V+ with V− at ground, unless otherwise noted.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: VS = ±5V (continued) At RL = 500Ω and VIN = single-ended input on V+ with V− at ground, unless otherwise noted. NOISE DENSITY vs CONTROL VOLTAGE 10000 Input-Referred Voltage Noise Density INPUT VOLTAGE AND CURRENT NOISE 10 RS = 20W on Each Input en (nV/?Hz) in (pA/?Hz) en (nV/?Hz) eO (nV/?Hz) 1000 100 Differential Input Voltage Noise (2.4nV/ÖHz) Output-Referred Voltage Noise Density 10 Current Noise (1.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 TYPICAL CHARACTERISTICS: VS = ±5V (continued) At RL = 500Ω and VIN = single-ended input on V+ with V− at ground, unless otherwise noted. GROUP DELAY vs GAIN GROUP DELAY vs FREQUENCY 10 10 9 8 8 Group Delay (ns) Group Delay (ns) VO = 1VPP RL = 500W VO = 1VPP RL = 500W 1MHz 7 6 5MHz 5 G = 0dB 6 G = +40dB 4 2 10MHz 4 0 -40 -30 -20 0 -10 10 20 30 1 40 Figure 19. Figure 20.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: VS = ±5V (continued) At RL = 500Ω and VIN = single-ended input on V+ with V− at ground, unless otherwise noted. GAIN CONTROL −PSRR AT MAX GAIN 6 5 5 4 4 Gain (dB) Gain (dB) GAIN CONTROL +PSRR AT MAX GAIN 6 3 2 2 1 1 0 0 1k 10k 100k 1M 10M 100M 1k Figure 26.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 APPLICATION INFORMATION CIRCUIT DESCRIPTION The VCA810 is a high gain adjust range, wideband, voltage amplifier with a voltage-controlled gain, as shown in Figure 29. The circuit’s basic voltage amplifier responds to the control of an internal gain-control amplifier. At its input, the voltage amplifier presents the high impedance of a differential stage, permitting flexible input impedance matching.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com RANGE-FINDING TGC AMPLIFIER The block diagram in Figure 31 illustrates the fundamental configuration common to pulse-echo range finding systems. A photodiode preamp provides an initial gain stage to the photodiode. 20W OPA657 VCA810 ADC and DSP 20kW 20W VC charging the holding capacitor. This charge drives the capacitor voltage in a positive direction, reducing the amplifier gain.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 STABILIZED WEIN-BRIDGE OSCILLATOR Adding Wein-bridge feedback to the above AGC amplifier produces an amplitude-stabilized oscillator. As Figure 34 shows, this alternative requires the addition of just two resistors (RW1, RW2) and two capacitors (CW1, CW2). Connecting the feedback network to the amplifier noninverting input introduces positive feedback to induce oscillation.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com LOW-DRIFT WIDEBAND LOG AMP The VCA810 can be used to provide a 2.5MHz (–3dB) log amp with low offset voltage and low gain drift. The exponential gain-control characteristic of the VCA810 permits simple generation of a temperature-compensated logarithmic response. Enclosing the exponential function in an op-amp feedback path inverts this function, producing the log response. Figure 35 shows the practical implementation of this technique.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 Zone III: VC < −2V. The VCA810 control pin is out of range, and some measure should be taken so that it does not exceed –2.5V. A limiting action could be achieved by using a voltage limiting amplifier. LOW-DRIFT, WIDEBAND EXPONENTIAL AMP A common use of the log amp above involves signal compounding. The inverse function, signal expanding, requires an exponential transfer function.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com For G > 1, the circuit applies a greater voltage to R2, increasing the feedback current this resistor supplies to the summing junction of the OPA820. The increased feedback current produces the same result as if R2 had been decreased in value in the basic circuit described above. Decreasing the effective R2 resistance moves the circuit pole to a higher G fP = 2 p R2C response frequency, producing the control.
PAGE 17
VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 Another factor limits the high-frequency performance of the resulting high-pass filter: the finite bandwidth of the op amp. This limits the frequency duration of the equalizer response. Limitations such as bandwidth and stability are clearly shown in Figure 42.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com C 0.047mF nR 5kW nR 5kW VO = VI VI R 330W s nRC G s s2 + nRC + 2 2 RC - 10-(V + 1) 2pRC C 1/2 OPA2822 fO = VO C 0.047mF BW = 50W R 330W 1/2 OPA2822 VOA 1 2pRC Q = n·10 -(VC + 1) VCA810 AO = -1 50W VC Figure 43. Tunable Band-Pass Filter 0 -5 -10 Gain (dB) -15 -20 -25 -30 -35 -40 -45 -50 100 1k 10k 100k Frequency (Hz) Figure 44.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 DESIGN-IN TOOLS MACROMODELS AND APPLICATIONS SUPPORT DEMONSTRATION BOARDS A printed circuit board (PCB) is available to assist in the initial evaluation of circuit performance using the VCA810. This evaluation board (EVM) is available free, as an unpopulated PCB delivered with descriptive documentation. The summary information for this board is shown in Table 1. Table 1.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com OUTPUT OFFSET ERROR OFFSET ADJUSTMENT Several elements contribute to the output offset voltage error; among them are the input offset voltage, the output offset voltage, the input bias current and the input offset current. To simplify the following analysis, the output offset voltage error is dependent only on the output-offset voltage of the VCA810 and the input offset voltage.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 GAIN CONTROL NOISE PERFORMANCE The VCA810 gain is controlled by means of a unipolar negative voltage applied between ground and the gain control input, pin 3. If use of the output disable feature is required, a ground-referenced bipolar voltage is needed. Output disable occurs for +0.15V ≤ VC ≤ +2V, and produces greater than 80dB of attenuation. The control voltage should be limited to +2V in disable mode, and –2.
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VCA810 SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 www.ti.com THERMAL ANALYSIS The VCA810 will not require heatsinking or airflow in most applications. Maximum desired junction temperature would set the maximum allowed internal power dissipation as described in this section. In no case should the maximum junction temperature be allowed to exceed +150°C.
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VCA810 www.ti.com SBOS275F – JUNE 2003 – REVISED DECEMBER 2010 INPUT AND ESD PROTECTION The VCA810 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. All pins on the VCA810 are internally protected from ESD by means of a pair of back-to-back, reverse-biased diodes to either power supply, as shown in Figure 49.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 28-Sep-2010 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties.
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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) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant VCA810AIDR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 VCA810IDR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 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) VCA810AIDR SOIC D 8 2500 367.0 367.0 35.0 VCA810IDR 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.