Datasheet LT1210X (Analog Devices) - 8

LT1210X PIN FUNCTIONS
V+ (Pins 1, 8, 9, 16, 17):
Positive Supply Voltage. V+ and off the biasing for the amplifier, reducing the quiescent V– must be chosen so that 10V ≤ (V+ – V–) < 36V. current to less than 200μA, or to control the quiescent
NC (Pins 2, 4, 5, 7, 10, 15):
No Connection. These pins current in normal operation. For more information, refer are floating, with no internal connection. to the Shutdown/Current Set section in the Applications Information.
OUT (Pin 3):
Amplifier Output. The output can source/sink a minimum of 1A over temperature.
COMP (Pin 13):
Adding a 0.01µF capacitor between the output and the COMP pin greatly reduces peaking when
-IN (Pin 6):
Inverting Input of Amplifier. Valid input range driving capacitive loads. To disconnect the optional com- is ±12V on ±15V supplies. pensation, leave the COMP pin open. For more infor-
+IN (Pin 11):
Non-Inverting Input of Amplifier. Valid input mation, refer to the Capacitive Loads section in the range is ±12V on ±15V supplies. Applications Information.
SHUTDOWN (Pin 12):
If the shutdown feature is not
V– (Pin 14):
Negative Supply Voltage. V+ and V– must be used, the SHUTDOWN pin must be connected to Ground chosen so that 10V ≤ (V+ – V–) < 36V. or V–. The SHUTDOWN pin can be used to either turn APPLICATIONS INFORMATION The LT1210X is a current feedback amplifier with high
Capacitive Loads
output current drive capability. The device is stable with The LT1210X includes an optional compensation network large capacitive loads and can easily supply the high cur- for driving capacitive loads. This network eliminates most rents required by capacitive loads. The amplifier will drive of the output stage peaking associated with capacitive low impedance loads such as cables with excellent linear- loads, allowing the frequency response to be flattened. ity at high frequencies. Figure 1 shows the effect of the network on a 200pF load.
Feedback Resistor Selection
Without the optional compensation, there is a 6dB peak at 40MHz caused by the effect of the capacitance on the The optimum value for the feedback resistors is a function output stage. Adding a 0.01µF bypass capacitor between of the operating conditions of the device, the load imped- the output and the COMP pins connects the compensation ance and the desired flatness of response. The Typical AC and greatly reduces the peaking. A lower value feedback Performance tables give the values which result in less resistor can now be used, resulting in a response which than 1dB of peaking for various resistive loads and oper- is flat to ±1dB to 40MHz. The network has the greatest ating conditions. If this level of flatness is not required, effect for CL in the range of 0pF to 1000pF. The graphs of a higher bandwidth can be obtained by use of a lower Bandwidth and Feedback Resistance vs Capacitive Load feedback resistor. The characteristic curves of Bandwidth can be used to select the appropriate value of feedback vs Supply Voltage indicate feedback resistors for peak- resistor. The values shown are for 1dB and 5dB peaking at ing up to 5dB. These curves use a solid line when the a gain of 2 with no resistive load. This is a worst-case con- response has less than 1dB of peaking and a dashed line dition, as the amplifier is more stable at higher gains and when the response has 1dB to 5dB of peaking. The curves with some resistive load in parallel with the capacitance. stop where the response has more than 5dB of peaking. Also shown is the –3dB bandwidth with the suggested For resistive loads, the COMP pin should be left open (see feedback resistor vs the load capacitance. Capacitive Loads section). 1210Xfa 8 For more information www.linear.com/LT1210X