Datasheet AD711 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | Precision, Low Cost, High Speed, BiFET Op Amp |
| Pages / Page | 17 / 10 — AD711. D/A CONVERTER APPLICATIONS. GUARDING. 5pF. TEXTRONIX 7A26. … |
| Revision | E |
| File Format / Size | PDF / 630 Kb |
| Document Language | English |
AD711. D/A CONVERTER APPLICATIONS. GUARDING. 5pF. TEXTRONIX 7A26. OSCILLOSCOPE. PREAMP. VERROR. INPUT SELECTION. 205. AD3554. HP2835. 20pF. 0.47
Text Version of Document
AD711
current-to-voltage converters. The use of a guarding technique such as that shown in Figure 7, in printed circuit board layout and construction is critical to minimize leakage currents. The guard ring is connected to a low impedance potential at the same level as the inputs. High impedance signal lines should not be extended for any unnecessary length on the printed circuit board.
4 5 4 5 3 6 2 6 3 2 7
Figure 5a. Settling Characteristics 0 to +10 V Step
8
Upper Trace: Output of AD711 Under Test (5 V/Div)
1 7 1
Lower Trace: Amplified Error Voltage (0.01%/Div)
8
Figure 7. Board Layout for Guarding Inputs
D/A CONVERTER APPLICATIONS
The AD711 is an excellent output amplifier for CMOS DACs. It can be used to perform both 2-quadrant and 4-quadrant operation. The output impedance of a DAC using an inverted R-2R ladder approaches R for codes containing many 1s, 3R for codes containing a single 1, and for codes containing all zero, the output impedance is infinite. For example, the output resistance of the AD7545 will modu- late between 11 kW and 33 kW. Therefore, with the DAC’s internal feedback resistance of 11 kW, the noise gain will vary Figure 5b. Settling Characteristics 0 to –10 V Step from 2 to 4/3. This changing noise gain modulates the effect of Upper Trace: Output of AD711 Under Test (5 V/Div) the input offset voltage of the amplifier, resulting in nonlinear Lower Trace: Amplified Error Voltage (0.01%/Div) DAC amplifier performance. The AD711K with guaranteed 500 mV offset voltage minimizes
GUARDING
this effect to achieve 12-bit performance. The low input bias current (15 pA) and low noise characteristics of the AD711 BiFET op amp make it suitable for electrometer applications such as photo diode preamplifiers and picoampere
5pF TEXTRONIX 7A26 OSCILLOSCOPE PREAMP VERROR 5 INPUT SELECTION 205 AD3554 HP2835 HP2835 1M 20pF 0.47 F 0.47 F 4.99k 4.99k 200k –15V +15V DATA DYNAMICS 5-18pF 10k 5109 1.1k V (OR IN 10k EQUIVALENT 0.2-0.0pF FLAT TOP 10k AD711 VOUT PULSE GENERATOR) 5k 10pF 0.1 F 0.1 F –15V +15V
Figure 6. Settling Time Test Circuit REV. E –9– Document Outline FEATURES PRODUCT DESCRIPTION CONNECTION DIAGRAMS PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE Typical Performance Characteristics OPTIMIZING SETTLING TIME OP AMP SETTLING TIME—A MATHEMATICAL MODEL GUARDING D/A CONVERTER APPLICATIONS NOISE CHARACTERISTICS DRIVING THE ANALOG INPUT OF AN A/D CONVERTER DRIVING A LARGE CAPACITIVE LOAD ACTIVE FILTER APPLICATIONS SECOND ORDER LOW PASS FILTER 9-POLE CHEBYCHEV FILTER OUTLINE DIMENSIONS Revision History
current-to-voltage converters. The use of a guarding technique such as that shown in Figure 7, in printed circuit board layout and construction is critical to minimize leakage currents. The guard ring is connected to a low impedance potential at the same level as the inputs. High impedance signal lines should not be extended for any unnecessary length on the printed circuit board.
4 5 4 5 3 6 2 6 3 2 7
Figure 5a. Settling Characteristics 0 to +10 V Step
8
Upper Trace: Output of AD711 Under Test (5 V/Div)
1 7 1
Lower Trace: Amplified Error Voltage (0.01%/Div)
8
Figure 7. Board Layout for Guarding Inputs
D/A CONVERTER APPLICATIONS
The AD711 is an excellent output amplifier for CMOS DACs. It can be used to perform both 2-quadrant and 4-quadrant operation. The output impedance of a DAC using an inverted R-2R ladder approaches R for codes containing many 1s, 3R for codes containing a single 1, and for codes containing all zero, the output impedance is infinite. For example, the output resistance of the AD7545 will modu- late between 11 kW and 33 kW. Therefore, with the DAC’s internal feedback resistance of 11 kW, the noise gain will vary Figure 5b. Settling Characteristics 0 to –10 V Step from 2 to 4/3. This changing noise gain modulates the effect of Upper Trace: Output of AD711 Under Test (5 V/Div) the input offset voltage of the amplifier, resulting in nonlinear Lower Trace: Amplified Error Voltage (0.01%/Div) DAC amplifier performance. The AD711K with guaranteed 500 mV offset voltage minimizes
GUARDING
this effect to achieve 12-bit performance. The low input bias current (15 pA) and low noise characteristics of the AD711 BiFET op amp make it suitable for electrometer applications such as photo diode preamplifiers and picoampere
5pF TEXTRONIX 7A26 OSCILLOSCOPE PREAMP VERROR 5 INPUT SELECTION 205 AD3554 HP2835 HP2835 1M 20pF 0.47 F 0.47 F 4.99k 4.99k 200k –15V +15V DATA DYNAMICS 5-18pF 10k 5109 1.1k V (OR IN 10k EQUIVALENT 0.2-0.0pF FLAT TOP 10k AD711 VOUT PULSE GENERATOR) 5k 10pF 0.1 F 0.1 F –15V +15V
Figure 6. Settling Time Test Circuit REV. E –9– Document Outline FEATURES PRODUCT DESCRIPTION CONNECTION DIAGRAMS PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE Typical Performance Characteristics OPTIMIZING SETTLING TIME OP AMP SETTLING TIME—A MATHEMATICAL MODEL GUARDING D/A CONVERTER APPLICATIONS NOISE CHARACTERISTICS DRIVING THE ANALOG INPUT OF AN A/D CONVERTER DRIVING A LARGE CAPACITIVE LOAD ACTIVE FILTER APPLICATIONS SECOND ORDER LOW PASS FILTER 9-POLE CHEBYCHEV FILTER OUTLINE DIMENSIONS Revision History
