LT1228 - 100MHz Current Feedback Amplifier with DC Gain Control
Features
- Very Fast Transconductance Amplifier Bandwidth: 75MHz
- Outputs Swing Within 0.8V of Supplies
- gm = 10 x ISET
- Low THD: 0.2% at 30mVRMS Input
- Wide ISET Range: 1µA to 1mA
- Very Fast Current Feedback Amplifier
- Bandwidth: 100MHz
- Slew Rate: 1000V/µs
- Output Drive Current: 30mA
- Differential Gain: 0.04%
- Differential Phase: 0.1°
- High Input Impedance: 25M Ohm, 6pF
- Wide Supply Range: ±2V to ±15V
- Inputs Common Mode to Within 1.5V of Supplies
- Supply Current: 7mA
- Available in 8-Lead PDIP and SOIC Packages
Typical Application
Description
TheLT1228 makes it easy to electronically control the gain of signals from DC to video frequencies. The LT1228 implements gain control with a transconductance amplifier (voltage to current) whose gain is proportional to an externally controlled current. A resistor is typically used to convert the output current to a voltage, which is then amplified with a current feedback amplifier. The LT1228 combines both amplifiers into an 8-pin package, and operates on any supply voltage from 4V (±2V) to 30V (±15V). A complete differential input, gain controlled amplifier can be implemented with the LT1228 and just a few resistors.
The LT1228 transconductance amplifier has a high impedance differential input and a current source output with wide output voltage compliance. The transconductance, gm, is set by the current that flows into Pin5, ISET . The small signal gm is equal to ten times the value of ISET and this relationship holds over several decades of set current. The voltage at Pin 5 is two diode drops above the negative supply, Pin 4.
The LT1228 current feedback amplifier has very high input impedance and therefore it is an excellent buffer for the output of the transconductance amplifier. The current feedback amplifier maintains its wide bandwidth over a wide range of voltage gains making it easy to interface the transconductance amplifier output to other circuitry. The current feedback amplifier is designed to drive low impedance loads, such as cables, with excellent linearity at high frequencies.
Packaging
CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.
For complete and up to date package information and drawings, please refer to our packaging page
| Part Number | Package | Code | Temp | Package Drawing |
RoHS |
|---|---|---|---|---|---|
| LT1228CN8#PBF | N-8 | N | C | 05-08-1510 (N8) | Yes |
| LT1228CS8#PBF | SO-8 | S8 | C | 05-08-1610 (S8) | Yes |
| LT1228CS8#TRPBF | SO-8 | S8 | C | 05-08-1610 (S8) | Yes |
| LT1228IN8#PBF | N-8 | N | I | 05-08-1510 (N8) | Yes |
| LT1228IS8#PBF | SO-8 | S8 | I | 05-08-1610 (S8) | Yes |
| LT1228IS8#TRPBF | SO-8 | S8 | I | 05-08-1610 (S8) | Yes |
Order Info
- Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
- Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
- Please refer to our general ordering information or the product datasheet for more details
Package Variations and Pricing
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LT1228CN8#PBF | N-8 | C | $4.58 | $3.75 | Yes | |
| LT1228CS8#PBF | SO-8 | C | $5.17 | $4.20 | Yes | |
| LT1228CS8#TRPBF | SO-8 | C | $4.26 | Yes | ||
| LT1228IN8#PBF | N-8 | I | $5.95 | $4.83 | Yes | |
| LT1228IS8#PBF | SO-8 | I | $5.95 | $4.83 | Yes | |
| LT1228IS8#TRPBF | SO-8 | I | $4.89 | Yes | ||
| Buy Now • Request Samples | ||||||
Demo Boards
Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.| Part Number | Description | Price | Documentation |
|---|---|---|---|
| DC417B | DIP8, MS8, S8, SOT23-6 | Multi-Footprint General Purpose Board for Single Op. Amp | $25.00 | |
| Buy Now | |||
Applications
- Video DC Restore (Clamp) Circuits
- Video Differential Input Amplifiers
- Video Keyer/Fader Amplifiers
- AGC Amplifiers
- Tunable Filters
- Oscillators
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Design Tools
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LT1228
Technical Support
- For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
- For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.
