Datasheet LT1207 (Analog Devices) - 8
| Fabricante | Analog Devices |
| Descripción | Dual 250mA/60MHz Current Feedback Amplifier |
| Páginas / Página | 16 / 8 — SI PLIFIED SCHE ATIC. APPLICATI. S I FOR ATIO. Capacitive Loads. Feedback … |
| Formato / tamaño de archivo | PDF / 326 Kb |
| Idioma del documento | Inglés |
SI PLIFIED SCHE ATIC. APPLICATI. S I FOR ATIO. Capacitive Loads. Feedback Resistor Selection
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LT1207
W W SI PLIFIED SCHE ATIC
V+ TO ALL CURRENT Q5 SOURCES Q10 Q2 D1 Q11 Q18 Q1 Q6 Q15 Q17 Q9 V– 1.25k V– 50Ω CC +IN –IN R COMP C OUTPUT V+ SHUTDOWN V+ Q12 Q3 Q8 Q16 Q14 Q4 D2 Q13 Q7 V – LT1207 • SS 1/2 LT1207 CURRENT FEEDBACK AMPLIFIER
O U U W U APPLICATI S I FOR ATIO
The LT1207 is a dual current feedback amplifier with high line when the response has 0.5dB to 5dB of peaking. The output current drive capability. The device is stable with curves stop where the response has more than 5dB of large capacitive loads and can easily supply the high peaking. currents required by capacitive loads. The amplifier will For resistive loads, the COMP pin should be left open (see drive low impedance loads such as cables with excellent section on capacitive loads). linearity at high frequencies.
Capacitive Loads Feedback Resistor Selection
Each amplifier in the LT1207 includes an optional com- The optimum value for the feedback resistors is a function pensation network for driving capacitive loads. This net- of the operating conditions of the device, the load imped- work eliminates most of the output stage peaking associ- ance and the desired flatness of response. The Typical AC ated with capacitive loads, allowing the frequency re- Performance tables give the values which result in the sponse to be flattened. Figure 1 shows the effect of the highest 0.1dB and 0.5dB bandwidths for various resistive network on a 200pF load. Without the optional compensa- loads and operating conditions. If this level of flatness is tion, there is a 5dB peak at 40MHz caused by the effect of not required, a higher bandwidth can be obtained by use the capacitance on the output stage. Adding a 0.01µF of a lower feedback resistor. The characteristic curves of bypass capacitor between the output and the COMP pins Bandwidth vs Supply Voltage indicate feedback resistors connects the compensation and completely eliminates the for peaking up to 5dB. These curves use a solid line when peaking. A lower value feedback resistor can now be used, the response has less than 0.5dB of peaking and a dashed resulting in a response which is flat to 0.35dB to 30MHz. 8
W W SI PLIFIED SCHE ATIC
V+ TO ALL CURRENT Q5 SOURCES Q10 Q2 D1 Q11 Q18 Q1 Q6 Q15 Q17 Q9 V– 1.25k V– 50Ω CC +IN –IN R COMP C OUTPUT V+ SHUTDOWN V+ Q12 Q3 Q8 Q16 Q14 Q4 D2 Q13 Q7 V – LT1207 • SS 1/2 LT1207 CURRENT FEEDBACK AMPLIFIER
O U U W U APPLICATI S I FOR ATIO
The LT1207 is a dual current feedback amplifier with high line when the response has 0.5dB to 5dB of peaking. The output current drive capability. The device is stable with curves stop where the response has more than 5dB of large capacitive loads and can easily supply the high peaking. currents required by capacitive loads. The amplifier will For resistive loads, the COMP pin should be left open (see drive low impedance loads such as cables with excellent section on capacitive loads). linearity at high frequencies.
Capacitive Loads Feedback Resistor Selection
Each amplifier in the LT1207 includes an optional com- The optimum value for the feedback resistors is a function pensation network for driving capacitive loads. This net- of the operating conditions of the device, the load imped- work eliminates most of the output stage peaking associ- ance and the desired flatness of response. The Typical AC ated with capacitive loads, allowing the frequency re- Performance tables give the values which result in the sponse to be flattened. Figure 1 shows the effect of the highest 0.1dB and 0.5dB bandwidths for various resistive network on a 200pF load. Without the optional compensa- loads and operating conditions. If this level of flatness is tion, there is a 5dB peak at 40MHz caused by the effect of not required, a higher bandwidth can be obtained by use the capacitance on the output stage. Adding a 0.01µF of a lower feedback resistor. The characteristic curves of bypass capacitor between the output and the COMP pins Bandwidth vs Supply Voltage indicate feedback resistors connects the compensation and completely eliminates the for peaking up to 5dB. These curves use a solid line when peaking. A lower value feedback resistor can now be used, the response has less than 0.5dB of peaking and a dashed resulting in a response which is flat to 0.35dB to 30MHz. 8