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Application Section

(Continued)

HIGH-GAIN SALLEN-KEY ACTIVE FILTERS

The LMH6624 is well suited for high gain Sallen-Key type of
active filters.

Figure 12

shows the 2

nd

order Sallen-Key low

pass filter topology. Using component predistortion methods
discussed in OA-21 enables the proper selection of compo-
nents for these high-frequency filters.

LOW NOISE MEGNETIC MEDIA EQUALIZER

The LMH6624 implements a high-performance low noise
equalizer for such application as magnetic tape channels as
shown in

Figure 13

. The circuit combines an integrator with

a bandpass filter to produce the low noise equalization. The
circuit’s simulated frequency response is illustrated in

Figure

14

.

LAYOUT CONSIDERATION

National Semiconductor suggests the copper patterns on the
evaluation boards listed below as a guide for high frequency
layout. These boards are also useful as an aid in device
testing and characterization. As is the case with all high-
speed amplifiers, accepted-practice RF design technique on
the PCB layout is mandatory. Generally, a good high fre-
quency layout exhibits a separation of power supply and
ground traces from the inverting input and output pins. Para-
sitic capacitances between these nodes and ground will
cause frequency response peaking and possible circuit os-
cillations (see Application Note OA-15 for more information).
Use high quality chip capacitors with values in the range of
1000pF to 0.1F for power supply bypassing. One terminal of
each chip capacitor is connected to the ground plane and the
other terminal is connected to a point that is as close as
possible to each supply pin as allowed by the manufacturer’s
design rules. In addition, connect a tantalum capacitor with a
value between 4.7µf and 10µF in parallel with the chip ca-
pacitor. Signal lines connecting the feedback and gain resis-
tors should be as short as possible to minimize inductance
and microstrip line effect. Place input and output termination
resistors as close as possible to the input/output pins. Traces
greater than 1 inch in length should be impedance matched
to the corresponding load termination.

20058929

FIGURE 11. Low Noise Integrator

20058930

FIGURE 12. Sallen-Key Active Filter Topology

20058931

FIGURE 13. Noise Magnetic Media Equalizer

20058932

FIGURE 14. Equalizer Frequency Response

LMH6624

www.national.com

16

Содержание LMH6624

Страница 1: ...H6624 is stable for closed loop gain of AV 10 or 10 AV LMH6624 is offered in SOT23 5 and SOIC 8 packages Features VS 6V TA 25 C AV 20 Typical values unless specified n Gain bandwidth 1 5GHz n Input voltage noise 0 92nV n Input offset voltage limit over temp 700uV n Slew rate 350V µs n Slew rate AV 10 400V µs n HD2 f 10MHz RL 100Ω 65dBc n HD3 f 10MHz RL 100Ω 80dBc n Supply voltage range dual supply...

Страница 2: ...namic Performance fCL 3dB BW VO 400mVPP 90 MHz SR Slew Rate Note 8 VO 2VPP AV 20 300 V µs VO 2VPP AV 10 360 tr Rise Time VO 400mV Step 10 to 90 4 1 ns tf Fall Time VO 400mV Step 10 to 90 4 1 ns ts Settling Time 0 1 VO 2VPP Step 15 ns Distortion and Noise Response en Input Referred Voltage Noise f 1MHz 0 95 nV in Input Referred Current Noise f 1MHz 2 3 pA HD2 2nd Harmonic Distortion fC 10MHz VO 1VP...

Страница 3: ...CM 0V AV 20 RF 500Ω RL 100Ω Boldface limits apply at the temperature extremes See Note 12 Symbol Parameter Conditions Min Note 6 Typ Note 5 Max Note 6 Units Dynamic Performance fCL 3dB BW VO 400mVPP 95 MHz SR Slew Rate Note 8 VO 2VPP AV 20 350 V µs VO 2VPP AV 10 400 tr Rise Time VO 400mV Step 10 to 90 3 7 ns tf Fall Time VO 400mV Step 10 to 90 3 7 ns ts Settling Time 0 1 VO 2VPP Step 14 ns Distort...

Страница 4: ...VCM 4 5 to 5 25V VCM 4 5 to 5 0V 90 87 95 dB Transfer Characteristics AVOL Large Signal Voltage Gain RL 100Ω VO 3V to 3V 77 72 81 dB Output Characteristics VO Output Swing RL 100Ω 4 4 4 3 4 9 V No Load 4 8 4 65 5 2 RO Output Impedance f 100KHz 10 mΩ ISC Output Short Circuit Current Sourcing to Ground VIN 200mV Note 3 Note 11 100 85 156 mA Sinking to Ground VIN 200mV Note 3 Note 11 100 85 156 IOUT ...

Страница 5: ... by dividing the change in parameter at temperature extremes into the total temperature change Note 8 Slew rate is the slowest of the rising and falling slew rates Note 9 Machine Model 0Ω in series with 200pF Note 10 Simulation results Note 11 Short circuit test is a momentary test Output short circuit duration is 1 5ms Note 12 Electrical table values apply only for factory testing conditions at t...

Страница 6: ...Peaking with Varying RF 20058950 20058917 Open Loop Frequency Response Over Temperature Open Loop Frequency Response Over Temperature 20058959 20058960 Frequency Response with Varying VS Frequency Response with Varying VS 20058913 20058914 LMH6624 www national com 6 ...

Страница 7: ...ponse Inverting Frequency Response 20058916 20058915 Non Inverting Frequency Response Non Inverting Frequency Response 20058904 20058903 Non Inverting Frequency Response Varying VIN Non Inverting Frequency Response Varying VIN 20058906 20058905 LMH6624 www national com 7 ...

Страница 8: ...Varying VIN Non Inverting Frequency Response Varying VIN 20058908 20058907 Frequency Response with Cap Loading Frequency Response with Cap Loading 20058940 20058941 Frequency Response with Cap Loading Frequency Response with Cap Loading 20058939 20058938 LMH6624 www national com 8 ...

Страница 9: ...teristics Continued Sourcing Current vs VOUT Sourcing Current vs VOUT 20058957 20058954 Sinking Current vs VOUT Sinking Current vs VOUT 20058958 20058956 VOS vs VSUPPLY IOS vs VSUPPLY 20058955 20058953 LMH6624 www national com 9 ...

Страница 10: ...inued Distortion vs Frequency Distortion vs Frequency 20058944 20058946 Distortion vs Frequency Distortion vs Gain 20058945 20058942 Distortion vs VOUT Peak to Peak Distortion vs VOUT Peak to Peak 20058943 20058947 LMH6624 www national com 10 ...

Страница 11: ... Signal Pulse Response Non Inverting Large Signal Pulse Response 20058909 20058910 Non Inverting Small Signal Pulse Response Non Inverting Small Signal Pulse Response 20058912 20058911 PSRR vs Frequency PSRR vs Frequency 20058948 20058949 LMH6624 www national com 11 ...

Страница 12: ...Typical Performance Characteristics Continued Input Referred CMRR vs Frequency Input Referred CMRR vs Frequency 20058901 20058902 LMH6624 www national com 12 ...

Страница 13: ... be isolated with at least a 25Ω series resistor As seen in Figure 2 bias current cancellation is accom plished for the inverting configuration by placing a resistor Rb on the non inverting input equal in value to the resis tance seen by the inverting input Rf Rg Rs Rb should to be no less than 25Ω for optimum LMH6624 performance A shunt capacitor can minimize the additional noise of Rb TOTAL INPU...

Страница 14: ...stitutions Equation 1 will yield an eni referred to the non inverting input Referring eni to the inverting input is easily accomplished by multiplying eni by the ratio of non inverting to inverting gains NOISE FIGURE Noise Figure NF is a measure of the noise degradation caused by an amplifier 3 The Noise Figure formula is shown in Equation 3 The addi tion of a terminating resistor RT reduces the e...

Страница 15: ...se sources in Figure 10 This plot indicates the expected total equivalent input current noise density ini for a given feedback resistance Rf The total equivalent output voltage noise density eno is ini Rf 5 LOW NOISE INTEGRATOR The LMH6624 implements a deBoo integrator shown in Figure 11 Positive feedback maintains integration linearity The LMH6624 s low input offset voltage and matched inputs all...

Страница 16: ...ut exhibits a separation of power supply and ground traces from the inverting input and output pins Para sitic capacitances between these nodes and ground will cause frequency response peaking and possible circuit os cillations see Application Note OA 15 for more information Use high quality chip capacitors with values in the range of 1000pF to 0 1F for power supply bypassing One terminal of each ...

Страница 17: ... of other critical components will affect the closed loop behavior of the stage because of the interaction of these resistors with parasitic capacitances These parasitic capacitors could either be inherent to the device or be a by product of the board layout and component placement Moreover a large resistor will also add more thermal noise to the signal path Either way keeping the resistor values ...

Страница 18: ...Physical Dimensions inches millimeters unless otherwise noted 5 Pin SOT23 NS Package Number MF05A 8 Pin SOIC NS Package Number M08A LMH6624 www national com 18 ...

Страница 19: ...e the failure of the life support device or system or to affect its safety or effectiveness National Semiconductor Americas Customer Support Center Email new feedback nsc com Tel 1 800 272 9959 National Semiconductor Europe Customer Support Center Fax 49 0 180 530 85 86 Email europe support nsc com Deutsch Tel 49 0 69 9508 6208 English Tel 44 0 870 24 0 2171 Français Tel 33 0 1 41 91 8790 National...

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