Datasheet AD8013 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | Single Supply, Low Power, Triple Video Amplifier |
| Pages / Page | 13 / 10 — AD8013. G = –10. 180. L = 150. PHASE. VS =. S = +5V. –90. GAIN. PHASE … |
| Revision | A |
| File Format / Size | PDF / 358 Kb |
| Document Language | English |
AD8013. G = –10. 180. L = 150. PHASE. VS =. S = +5V. –90. GAIN. PHASE SHIFT – Degrees. S =. CLOSED-LOOP GAIN. (NORMALIZED) – dB. –61M. 10M. 100M
Text Version of Document
AD8013
To estimate the –3 dB bandwidth for closed-loop gains of 2 or greater, for feedback resistors not listed in the following table,
G = –10
the following single pole model for the AD8013 may be used:
R 180 L = 150
Ω
PHASE
G
VS =
±
5V 90
ACL . +
V
1 + SC (R Gn rin )
S = +5V
T F
+1 0
where: CT = transcapacitance > 1 pF
0 –90 GAIN
RF = feedback resistor
–1 PHASE SHIFT – Degrees
G = ideal closed loop gain
–2
Gn = 1 + RF
–3 V
R = noise gain
S =
±
5V
G
V S = +5V –4
rin = inverting input resistance > 150 Ω
CLOSED-LOOP GAIN (NORMALIZED) – dB
ACL = closed loop gain
–5
The –3 dB bandwidth is determined from this model as:
–61M 10M 100M 1G FREQUENCY – Hz
1 f3 . 2 π C (R + Gn rin) T F Figure 27. Closed-Loop Gain and Phase vs. Frequency, This model will predict –3 dB bandwidth to within about 10% G = –10, RL = 150 Ω to 15% of the correct value when the load is 150 Ω and VS = ±5 V. For lower supply voltages there will be a slight decrease in
General
bandwidth. The model is not accurate enough to predict either The AD8013 is a wide bandwidth, triple video amplifier that the phase behavior or the frequency response peaking of the offers a high level of performance on less than 4.0 mA per AD8013. amplifier of quiescent supply current. The AD8013 uses a It should be noted that the bandwidth is affected by attenuation proprietary enhancement of a conventional current feedback due to the finite input resistance. Also, the open-loop output architecture, and achieves bandwidth in excess of 200 MHz with resistance of about 12 Ω reduces the bandwidth somewhat when low differential gain and phase errors, making it an extremely driving load resistors less than about 250 Ω. (Bandwidths will efficient video amplifier. be about 10% greater for load resistances above a few hundred The AD8013’s wide phase margin coupled with a high output ohms.) short circuit current make it an excellent choice when driving any capacitive load. High open-loop gain and low inverting
Table I. –3 dB Bandwidth vs. Closed-Loop Gain and Feedback
input bias current enable it to be used with large values of
Resistor, RL = 150
Ω
(SOIC)
feedback resistor with very low closed-loop gain errors.
VS – Volts Gain RF – Ohms BW – MHz
It is designed to offer outstanding functionality and performance ±5 +1 2000 230 at closed-loop inverting or noninverting gains of one or greater. +2 845 (931) 150 (135) +10 301 80
Choice of Feedback & Gain Resistors
–1 698 (825) 140 (130) Because it is a current feedback amplifier, the closed-loop band- –10 499 85 width of the AD8013 may be customized using different values +5 +1 2000 180 of the feedback resistor. Table I shows typical bandwidths at +2 887 (931) 120 (130) different supply voltages for some useful closed-loop gains when +10 301 75 driving a load of 150 Ω. –1 698 (825) 130 (120) The choice of feedback resistor is not critical unless it is –10 499 80 important to maintain the widest, flattest frequency response.
Driving Capacitive Loads
The resistors recommended in the table are those (chip When used in combination with the appropriate feedback resistors) that will result in the widest 0.1 dB bandwidth without resistor, the AD8013 will drive any load capacitance without peaking. In applications requiring the best control of bandwidth, oscillation. The general rule for current feedback amplifiers is 1% resistors are adequate. Package parasitics vary between the that the higher the load capacitance, the higher the feedback 14-pin plastic DIP and the 14-pin plastic SOIC, and may result resistor required for stable operation. Due to the high open-loop in a slight difference in the value of the feedback resistor used to transresistance and low inverting input current of the AD8013, achieve the optimum dynamic performance. Resistor values and the use of a large feedback resistor does not result in large closed- widest bandwidth figures are shown in parenthesis for the SOIC loop gain errors. Additionally, its high output short circuit current where they differ from those of the DIP. Wider bandwidths than makes possible rapid voltage slewing on large load capacitors. those in the table can be attained by reducing the magnitude of the feedback resistor (at the expense of increased peaking), For the best combination of wide bandwidth and clean pulse while peaking can be reduced by increasing the magnitude of response, a small output series resistor is also recommended. the feedback resistor. Table II contains values of feedback and series resistors which result in the best pulse responses. Figure 29 shows the AD8013 Increasing the feedback resistor is especially useful when driving driving a 300 pF capacitor through a large voltage step with large capacitive loads as it will increase the phase margin of the virtually no overshoot. (In this case, the large and small signal closed-loop circuit. (Refer to the section on driving capacitive pulse responses are quite similar in appearance.) loads for more information.) REV. A –9–
To estimate the –3 dB bandwidth for closed-loop gains of 2 or greater, for feedback resistors not listed in the following table,
G = –10
the following single pole model for the AD8013 may be used:
R 180 L = 150
Ω
PHASE
G
VS =
±
5V 90
ACL . +
V
1 + SC (R Gn rin )
S = +5V
T F
+1 0
where: CT = transcapacitance > 1 pF
0 –90 GAIN
RF = feedback resistor
–1 PHASE SHIFT – Degrees
G = ideal closed loop gain
–2
Gn = 1 + RF
–3 V
R = noise gain
S =
±
5V
G
V S = +5V –4
rin = inverting input resistance > 150 Ω
CLOSED-LOOP GAIN (NORMALIZED) – dB
ACL = closed loop gain
–5
The –3 dB bandwidth is determined from this model as:
–61M 10M 100M 1G FREQUENCY – Hz
1 f3 . 2 π C (R + Gn rin) T F Figure 27. Closed-Loop Gain and Phase vs. Frequency, This model will predict –3 dB bandwidth to within about 10% G = –10, RL = 150 Ω to 15% of the correct value when the load is 150 Ω and VS = ±5 V. For lower supply voltages there will be a slight decrease in
General
bandwidth. The model is not accurate enough to predict either The AD8013 is a wide bandwidth, triple video amplifier that the phase behavior or the frequency response peaking of the offers a high level of performance on less than 4.0 mA per AD8013. amplifier of quiescent supply current. The AD8013 uses a It should be noted that the bandwidth is affected by attenuation proprietary enhancement of a conventional current feedback due to the finite input resistance. Also, the open-loop output architecture, and achieves bandwidth in excess of 200 MHz with resistance of about 12 Ω reduces the bandwidth somewhat when low differential gain and phase errors, making it an extremely driving load resistors less than about 250 Ω. (Bandwidths will efficient video amplifier. be about 10% greater for load resistances above a few hundred The AD8013’s wide phase margin coupled with a high output ohms.) short circuit current make it an excellent choice when driving any capacitive load. High open-loop gain and low inverting
Table I. –3 dB Bandwidth vs. Closed-Loop Gain and Feedback
input bias current enable it to be used with large values of
Resistor, RL = 150
Ω
(SOIC)
feedback resistor with very low closed-loop gain errors.
VS – Volts Gain RF – Ohms BW – MHz
It is designed to offer outstanding functionality and performance ±5 +1 2000 230 at closed-loop inverting or noninverting gains of one or greater. +2 845 (931) 150 (135) +10 301 80
Choice of Feedback & Gain Resistors
–1 698 (825) 140 (130) Because it is a current feedback amplifier, the closed-loop band- –10 499 85 width of the AD8013 may be customized using different values +5 +1 2000 180 of the feedback resistor. Table I shows typical bandwidths at +2 887 (931) 120 (130) different supply voltages for some useful closed-loop gains when +10 301 75 driving a load of 150 Ω. –1 698 (825) 130 (120) The choice of feedback resistor is not critical unless it is –10 499 80 important to maintain the widest, flattest frequency response.
Driving Capacitive Loads
The resistors recommended in the table are those (chip When used in combination with the appropriate feedback resistors) that will result in the widest 0.1 dB bandwidth without resistor, the AD8013 will drive any load capacitance without peaking. In applications requiring the best control of bandwidth, oscillation. The general rule for current feedback amplifiers is 1% resistors are adequate. Package parasitics vary between the that the higher the load capacitance, the higher the feedback 14-pin plastic DIP and the 14-pin plastic SOIC, and may result resistor required for stable operation. Due to the high open-loop in a slight difference in the value of the feedback resistor used to transresistance and low inverting input current of the AD8013, achieve the optimum dynamic performance. Resistor values and the use of a large feedback resistor does not result in large closed- widest bandwidth figures are shown in parenthesis for the SOIC loop gain errors. Additionally, its high output short circuit current where they differ from those of the DIP. Wider bandwidths than makes possible rapid voltage slewing on large load capacitors. those in the table can be attained by reducing the magnitude of the feedback resistor (at the expense of increased peaking), For the best combination of wide bandwidth and clean pulse while peaking can be reduced by increasing the magnitude of response, a small output series resistor is also recommended. the feedback resistor. Table II contains values of feedback and series resistors which result in the best pulse responses. Figure 29 shows the AD8013 Increasing the feedback resistor is especially useful when driving driving a 300 pF capacitor through a large voltage step with large capacitive loads as it will increase the phase margin of the virtually no overshoot. (In this case, the large and small signal closed-loop circuit. (Refer to the section on driving capacitive pulse responses are quite similar in appearance.) loads for more information.) REV. A –9–
