FPGA可编程逻辑器件芯片AD823AARZ-R7中文规格书 - 图文

Data Sheet

FEATURES

Single-supply operation Output swings rail-to-rail

Input voltage range extends below ground Single-supply capability from 3 V to 36 V High load drive

Capacitive load drive of 470 pF (G = +1, 25% overshoot) Linear output current of 40 mA, 0.5 V from supplies Excellent ac performance on 2.6 mA/amplifier ?3 dB bandwidth of 17 MHz, G = +1 325 ns settling time to 0.01% (2 V step) Slew rate of 30 V/μs

Low distortion: ?108 dBc at 20 kHz (G = ?1, RL = 2 kΩ) Good dc performance

700 μV maximum input offset voltage 1 μV/°C offset voltage drift

25 pA maximum input bias current Low noise: 14 nV/√Hz at 10 kHz

No phase inversion with inputs to the supply rails

APPLICATIONS

Photodiode preamps Active filters

12-bit to 16-bit data acquisition systemsMedical instrumentation Precision instrumentation

GENERAL DESCRIPTION

The AD823A is a dual precision, 17 MHz, JFET input op amp manufactured in the extra fast complementary bipolar (XFCB) process. The AD823A can operate from a single supply of 3 V to 36 V or from dual supplies of ±1.5 V to ±18 V. It has true single-supply capability with an input voltage range extending below ground in single-supply mode. Output voltage swing extends to within 20 mV of each rail for IOUT ≤ 100 μA, providing outstanding output dynamic range. It also has a linear output current of 40 mA, 0.5 V from the supply rails.

An offset voltage of 700 μV maximum, an offset voltage drift of 1 μV/°C, and typical input bias currents of 0.3 pA provide dc precision with source impedances up to 1 GΩ. The AD823A provides 17 MHz, ?3 dB bandwidth, and a 30 V/μs slew rate with a low supply current of only 2.6 mA per amplifier. It also provides low input voltage noise of 14 nV/√Hz and ?108 dB SFDR at 20 kHz. The AD823A has low input capacitances (0.6 pF differ-ential and 1.3 pF common mode) and drives more than 500 pF of direct capacitive load as a follower. This lets the amplifier handle a wide range of load conditions.

AD823A

CONNECTION DIAGRAM

OUT118+VS–IN127OUT2+IN136–IN2–V1S45+IN200-AD823A93490Figure 1. 8-Lead SOIC

AD823AOUT118+VS–IN127OUT2+IN136–IN2–VS45+IN2201-9(Not to Scale)TOP VIEW3490Figure 2. 8-Lead MSOP

VS = 3VCL = 50pFG = +13.0V1.5V0V940-500mV/DIV200μs/DIV93490

Figure 3. Output Swing, +VS = +3 V, G = +1

This combination of ac and dc performance, plus the outstanding load drive capability, results in an exceptionally versatile ampli-fier for applications such as ADC drivers, high speed active filters, and other low voltage, high dynamic range systems.

The AD823A is available over the industrial temperature range of ?40°C to +85°C and is offered in an 8-lead SOIC package and an 8-lead MSOP package.

Data Sheet

OPEN-LOOP GAINOPEN-LOOP GAINAD823A

|A| (dB)fxG = R2C1sG = 1log ffpfu|A (s)|I TO V GAINfzfxfnG = 1 + CS/CFG = 1fpG = RFCS(s)ffu0°90°–45°45°PHASE (°)–90°log f0°f–135°–45°–180°–90°09439-400(A) WITHOUT COMPENSATION–135°(B) WITH COMPENSATIONFigure 43. Gain and Phase Plot of the Transimpedance Amplifier Design

The dominant sources of output noise in the wideband

photodiode preamp design are the input voltage noise of the amplifier, VNOISE and the resistor noise due to RF. The gray curve in Figure 43 shows the noise gain over frequencies for the

photodiode preamp. The noise bandwidth is at the frequency fN, and it can be calculated by

1.2pF49.9k?+5V–5V0.1μFfN=

fu

AD823AVOUT0.1μF100?09439-050(CS+CF)CF

(6)

TRANSIMPEDANCE GAIN (dB)Figure 44 shows the AD823A configured as a transimpedance photodiode amplifier. The amplifier is used in conjunction with a photodiode detector with input capacitance of 5 pF. Figure 45 shows the transimpedance response of the AD823A when IPHOTO is 1 μA p-p. The amplifier has a bandwidth of 2.2 MHz when it is maximized for a 45° phase margin with CF = 1.2 pF. Note that with the PCB parasitics added to CF, the peaking is only 0.5 dB and the bandwidth is slightly reduced. Increasing CF to 2.7 pF completely eliminates the peaking. However, it reduces the bandwidth to 1.2 MHz.

Table 8 shows the noise sources and total output noise for the photodiode preamp, where the preamplifier is configured to have a 45° phase margin for maximal bandwidth and fz = fx = fn in this case.

–5VFigure 44. Photodiode Preamplifier

9594939291908988878609439-144IPHOTO = 1μA p-pCF = 2.7pFIPHOTO = 1μA p-pCF = 1.2pF851k10k100kFREQUENCY (Hz)1M10MFigure 45. Photodiode Preamplifier Frequency Response

Rev. B | Page 17 of 20

AD823A

Table 8. RMS Noise Contributions of Photodiode Preamp ContributorRF VNOISE ExpressionData Sheet

(μV)1 55.17 4kT?RF?fN?π2VNOISE?RSSTotal?CS?CM?CF?2CD?CF?π2?fN138.5 149.1 1

RMS noise with RF = 50 kΩ, CS = 5 pF, CF = 1.2 pF, CM = 1.3 pF, and CD = 0.6 pF.

ACTIVE FILTER

The AD823A is an ideal candidate for an active filter because of its low input bias current and its low input capacitance. Low input bias current reduces dc error in the signal path while low input capacitance improves the accuracy of the active filter. As a general rule of thumb, the bandwidth of the amplifier should be at least 10 times bigger than the cutoff frequency of the filter implemented. Therefore, the AD823A is capable of implementing active filters of up to 1.7 MHz.

C1200pF+VSFigure 47 shows the two-pole Butterworth active filter’s response. Note that it has a maximally flat pass band, a ?3 dB bandwidth of 1 MHz, and a 12 dB/octave roll-off in the stop band. The cutoff frequency (fc) and the Q factor of the Butterworth filter can be calculated by:

fc?

12?R1R2C1C2

R1R2C1C2

(7)

Q?

?R1?R2??C2

(8)

VINR11.12k?RT49.9?R21.12k?C2100pFAD823AVOUT09439-146–VS

Therefore, one can easily adjust the cutoff frequency by appropriately factoring the resistor and capacitor values. For example, a 100 kHz filter can be implemented by increasing the values of R1 and R2 by 10 times. Note that the Q factor remains the same in this case.

Figure 46. Two-Pole Sallen-Key Active Filter

Figure 46 shows an example of a second-order Butterworth filter, which is implemented by the Sallen-Key topology. This structure can be duplicated to produce higher-order filters.

30–3–6MAGNITUDE (dB)–9–12–15–18–21–24–27–30–331k10k100k1M10M09439-147–36100FREQUENCY (Hz)Figure 47. Two-Pole Butterworth Active Filter Response

Rev. B | Page 18 of 20

Data Sheet

MAXIMIZING PERFORMANCE THROUGH PROPER LAYOUT

To achieve the maximum performance of the extremely high input impedance and low offset voltage of the AD823A, care should be taken in the circuit board layout. The PCB surface must remain clean and free of moisture to avoid leakage currents between adjacent traces. Surface coating of the circuit board reduces surface moisture and provides a humidity barrier, reducing parasitic resistance on the board. The use of guard rings around the amplifier inputs further reduces leakage currents. Figure 48 shows how the guard rings should be configured, and Figure 49 shows the top view of how a surface-mount layout can be arranged. The guard ring does not need to be a specific width, but it should form a continuous loop around both inputs. By setting the guard ring voltage equal to the voltage at the non-inverting input, parasitic capacitance is minimized as well. For further reduction of leakage currents, components can be mounted to the PCB using Teflon? standoff insulators.

VINVOUTAD823A

VOUTVINAD823AAD823AVINVOUTAD823AFigure 48. Guard Ring Layout and Connections to

Reduce PCB Leakage Currents

V+R1VIN1VIN2GUARDRINGGUARDRINGV–R2AD823AR2R1VREFVREFFigure 49. Top View of AD823A SOIC Layout with Guard Rings

Rev. B | Page 19 of 20

09439-15309439-152AD823A

OUTLINE DIMENSIONS

5.00(0.1968)4.80(0.1890)4.00(0.1574)3.80(0.1497)8154Data Sheet

6.20(0.2441)5.80(0.2284)1.27(0.0500)BSC0.25(0.0098)0.10(0.0040)COPLANARITY0.10SEATINGPLANE1.75(0.0688)1.35(0.0532)0.50(0.0196)0.25(0.0099)8°0°0.25(0.0098)0.17(0.0067)1.27(0.0500)0.40(0.0157)45°0.51(0.0201)0.31(0.0122)COMPLIANTTOJEDECSTANDARDSMS-012-AACONTROLLINGDIMENSIONSAREINMILLIMETERS;INCHDIMENSIONS(INPARENTHESES)AREROUNDED-OFFMILLIMETEREQUIVALENTSFORREFERENCEONLYANDARENOTAPPROPRIATEFORUSEINDESIGN.Figure 50. 8-Lead Standard Small Outline Package [SOIC_N]

Narrow Body

(R-8)

Dimensions shown in millimeters and (inches)

3.203.002.803.203.002.80PIN1IDENTIFIER8515.154.904.6540.65BSC0.950.850.750.150.05COPLANARITY0.100.400.2515°MAX1.10MAX0.230.090.800.550.4010-07-2009-B6°0°COMPLIANTTOJEDECSTANDARDSMO-187-AAFigure 51. 8-Lead Mini Small Outline Package [MSOP]

(RM-8)

Dimensions shown in millimeters

ORDERING GUIDE

Models1 AD823AARZ AD823AARZ-RL AD823AARZ-R7 AD823AARMZ AD823AARMZ-R7 AD823A-2AR-EBZ AD823A-2ARM-EBZ

1

Temperature Range ?40°C to +85°C ?40°C to +85°C ?40°C to +85°C ?40°C to +85°C ?40°C to +85°C

Package Description 8-Lead SOIC_N

8-Lead SOIC_N, 13” Tape and Reel 8-Lead SOIC_N, 7” Tape and Reel 8-lead MSOP

8-lead MSOP, 7” Tape and Reel Evaluation Board for 8-Lead SOIC Evaluation Board for 8-Lead MSOP

Package Option R-8 R-8 R-8 RM-8 RM-8

012407-ABranding

H34 H34

Z = RoHS Compliant Part.