Datasheet AD8014 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | 400 MHz, Low Power, High Performance Amplifier |
| Pages / Page | 12 / 10 — AD8014. Video Drivers. DRIVING CAPACITIVE LOADS. 0.00. 0.02 0.04. 0.05 … |
| Revision | C |
| File Format / Size | PDF / 1.3 Mb |
| Document Language | English |
AD8014. Video Drivers. DRIVING CAPACITIVE LOADS. 0.00. 0.02 0.04. 0.05 0.05. 0.05. 0.04. 0.04 0.04. 0.03. 0.10. –0.05 –0.10
Text Version of Document
AD8014 Video Drivers DRIVING CAPACITIVE LOADS
The AD8014 easily drives series terminated cables with video The AD8014 was designed primarily to drive nonreactive loads. signals. Because the AD8014 has such good output drive you If driving loads with a capacitive component is desired, best can parallel two or three cables driven from the same AD8014. settling response is obtained by the addition of a small series Figure 23 shows the differential gain and phase driving one resistance as shown in Figure 26. The accompanying graph video cable. Figure 24 shows the differential gain and phase shows the optimum value for RSERIES vs. Capacitive Load. It is driving two video cables. Figure 25 shows the differential gain worth noting that the frequency response of the circuit when and phase driving three video cables. driving large capacitive loads will be dominated by the passive roll-off of RSERIES and CL.
0.00 0.02 0.04 0.05 0.05 0.05 0.04 0.04 0.04 0.04 0.03 0.10 40 0.05 0.00 –0.05 –0.10 30 DIFFERENTIAL GAIN – %
V
0.00 0.01 0.10 0.21 0.26 0.28 0.29 0.30 0.30 0.30 0.30 0.60 – 0.40 0.20 0.00 R SERIES –0.20 20 DIFFERENTIAL –0.40 PHASE – Degrees –0.60 1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
Figure 23. Differential Gain and Phase RF = 500, ±5 V, RL =
10
150 Ω, Driving One Cable, G = +2
0 5 10 15 20 25 CL – pF
Figure 26. Driving Capacitive Load
0.00 –0.02 0.03 0.05 0.06 0.06 0.05 0.05 0.07 0.10 0.14 0.30 Choosing Feedback Resistors 0.20 0.10
Changing the feedback resistor can change the performance of
0.00
the AD8014 like any current feedback op amp. The table below
–0.10 –0.20
illustrates common values of the feedback resistor and the per-
–0.30
formance which results.
DIFFERENTIAL GAIN – % 0.00 0.07 0.24 0.40 0.43 0.44 0.43 0.40 0.35 0.26 0.16 0.60 0.40 Table II. 0.20 0.00 –3 dB BW –3 dB BW –0.20 –0.40 VO =
ⴞ
0.2 V VO =
ⴞ
0.2 V DIFFERENTIAL PHASE – Degrees –0.60 Gain RF RG RL = 1 k
⍀
RL = 150
⍀
1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
+1 1 kΩ Open 480 430 Figure 24. Differential Gain and Phase RF = 500, ±5 V, RL = +2 1 kΩ 1 kΩ 280 260 75 Ω, Driving Two Cables, G = +2 +10 1 kΩ 111 Ω 50 45 –1 1 kΩ 1 kΩ 160 150
0.00 0.44 0.52 0.54 0.52 0.52 0.50 0.48 0.47 0.44 0.45
–2 1 kΩ 499 Ω 140 130
0.80 0.60
–10 1 kΩ 100 Ω 45 40
0.40 0.20
+2 2 kΩ 2 kΩ 200* 180*
0.00
+2 750 Ω 750 Ω 260* 210*
–0.20 –0.40
+2 499 Ω 499 Ω 280* 230*
–0.60 –0.80
*V
DIFFERENTIAL GAIN – %
O = ± 1 V.
0.00 0.10 0.32 0.53 0.57 0.59 0.58 0.56 0.54 0.51 0.48 0.80 0.60 0.40 0.20 0.00 –0.20 –0.40 DIFFERENTIAL –0.60 PHASE – Degrees –0.80 1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
Figure 25. Differential Gain and Phase RF = 500, ±5 V, RL = 50 Ω, Driving Three Cables, G = +2 Rev. C –9–
The AD8014 easily drives series terminated cables with video The AD8014 was designed primarily to drive nonreactive loads. signals. Because the AD8014 has such good output drive you If driving loads with a capacitive component is desired, best can parallel two or three cables driven from the same AD8014. settling response is obtained by the addition of a small series Figure 23 shows the differential gain and phase driving one resistance as shown in Figure 26. The accompanying graph video cable. Figure 24 shows the differential gain and phase shows the optimum value for RSERIES vs. Capacitive Load. It is driving two video cables. Figure 25 shows the differential gain worth noting that the frequency response of the circuit when and phase driving three video cables. driving large capacitive loads will be dominated by the passive roll-off of RSERIES and CL.
0.00 0.02 0.04 0.05 0.05 0.05 0.04 0.04 0.04 0.04 0.03 0.10 40 0.05 0.00 –0.05 –0.10 30 DIFFERENTIAL GAIN – %
V
0.00 0.01 0.10 0.21 0.26 0.28 0.29 0.30 0.30 0.30 0.30 0.60 – 0.40 0.20 0.00 R SERIES –0.20 20 DIFFERENTIAL –0.40 PHASE – Degrees –0.60 1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
Figure 23. Differential Gain and Phase RF = 500, ±5 V, RL =
10
150 Ω, Driving One Cable, G = +2
0 5 10 15 20 25 CL – pF
Figure 26. Driving Capacitive Load
0.00 –0.02 0.03 0.05 0.06 0.06 0.05 0.05 0.07 0.10 0.14 0.30 Choosing Feedback Resistors 0.20 0.10
Changing the feedback resistor can change the performance of
0.00
the AD8014 like any current feedback op amp. The table below
–0.10 –0.20
illustrates common values of the feedback resistor and the per-
–0.30
formance which results.
DIFFERENTIAL GAIN – % 0.00 0.07 0.24 0.40 0.43 0.44 0.43 0.40 0.35 0.26 0.16 0.60 0.40 Table II. 0.20 0.00 –3 dB BW –3 dB BW –0.20 –0.40 VO =
ⴞ
0.2 V VO =
ⴞ
0.2 V DIFFERENTIAL PHASE – Degrees –0.60 Gain RF RG RL = 1 k
⍀
RL = 150
⍀
1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
+1 1 kΩ Open 480 430 Figure 24. Differential Gain and Phase RF = 500, ±5 V, RL = +2 1 kΩ 1 kΩ 280 260 75 Ω, Driving Two Cables, G = +2 +10 1 kΩ 111 Ω 50 45 –1 1 kΩ 1 kΩ 160 150
0.00 0.44 0.52 0.54 0.52 0.52 0.50 0.48 0.47 0.44 0.45
–2 1 kΩ 499 Ω 140 130
0.80 0.60
–10 1 kΩ 100 Ω 45 40
0.40 0.20
+2 2 kΩ 2 kΩ 200* 180*
0.00
+2 750 Ω 750 Ω 260* 210*
–0.20 –0.40
+2 499 Ω 499 Ω 280* 230*
–0.60 –0.80
*V
DIFFERENTIAL GAIN – %
O = ± 1 V.
0.00 0.10 0.32 0.53 0.57 0.59 0.58 0.56 0.54 0.51 0.48 0.80 0.60 0.40 0.20 0.00 –0.20 –0.40 DIFFERENTIAL –0.60 PHASE – Degrees –0.80 1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
Figure 25. Differential Gain and Phase RF = 500, ±5 V, RL = 50 Ω, Driving Three Cables, G = +2 Rev. C –9–
