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Home > Products > Integrated Circuits (ICs) > Linear > Instrumentation, Op Amps, Buffer Amps

Texas Instruments ACF2101BUG4

Name: ACF2101BUG4
Brand: Texas Instruments
SKU: ACF2101BUG4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ACF2101BUG4

Manufacturer:: Texas Instruments

Category:: Instrumentation, Op Amps, Buffer Amps

Package:: 24-SOIC (0.295", 7.50mm Width)

Datasheet:: ACF2101BUG4.pdf

Description:: IC SW INTEG 2 CIRCUIT 24SOIC

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Product details

Overview

ACF2101BUG4 from Burr-Brown (now Texas Instruments) is a dual precision switched integrator IC designed for low-noise current-to-voltage conversion in scientific instrumentation. It features integrated 100pF capacitors, TTL-compatible digital control inputs (Hold/Reset/Select), ±100µA input current range, 10µVrms output noise in Hold/Reset modes, and operates on ±5V to ±18V supplies. It is used in photodiode front ends and CT scanner signal conditioning.

For engineers reviewing the ACF2101BUG4 datasheet, ACF2101BUG4 pinout, ACF2101BUG4 application, or ACF2101BUG4 equivalent, this page delivers verified specifications, SOIC-24 pin mapping, real-world integration use cases, and validated alternative parts - all grounded in the original Burr-Brown PDS-1078D datasheet and TI packaging documentation.

Technical Context

The ACF2101BUG4 implements two independent switched-capacitor integrators with Difet® amplifier cores, each supporting Integrate/Hold/Reset operational modes controlled by three TTL-level digital inputs per channel. Its architecture eliminates external feedback resistors and relies on precise internal 100pF integration capacitors (±2% accuracy, –50 to 0 ppm/°C tempco).

Each channel includes dedicated Sw In, In, Cap, Com, Sw Com, Sw Out, Out, Hold, Reset, and Select terminals, with active laser trimming for offset (±2mV) and drift (±5µV/°C). The device achieves 120dB dynamic range and 0.1pC charge transfer error between Integrate and Reset modes - critical for high-fidelity charge measurement.

Key Specifications

Parameter	Value and Actual Design Meaning
Input Current Range	±100 µA per channel - supports precision photodiode and sensor current signals without external scaling.
Integration Capacitor	100 pF internal (±2% tolerance) - enables fixed-gain I-to-V conversion with no external capacitor required.
Output Noise (Hold/Reset)	10 µVrms (BW = 0.1Hz–250kHz) - ensures sub-microvolt stability during signal hold periods.
Charge Transfer Error	0.1 pC (Reset→Integrate) - limits voltage offset to 1 mV when using internal 100pF capacitor.
Bias Current	100 fA typical - minimizes leakage-induced integration error in high-impedance current sources.
Supply Voltage Range	+4.5V to +18V / –10V to –18V - allows flexible biasing including standard ±15V industrial rails.
Operating Temperature	–40°C to +85°C (spec), –40°C to +125°C (operation) - qualified for medical and industrial environments.

Pinout & Package

ACF2101BUG4 is housed in a 24-pin plastic SOIC (DW) package with 1.27 mm pitch, JEDEC MS-013 compliant, moisture sensitivity level (MSL) 3 (260°C peak reflow, 168 hr floor life).

Pin/Terminal	Circuit Role	Design Meaning
1	Sw In B	Switched input for Channel B - connects input current through Hold switch before summing junction.
2	In B	Direct input for Channel B - bypasses Hold switch for continuous integration or low-latency paths.
3	Cap B	External integration capacitor connection for Channel B - ties to external C_EXT if augmenting internal 100pF.
4	Com B	Analog common reference for Channel B - must be tied to system analog ground or guard plane.
5	Gnd B	Ground return for Channel B amplifier - separate from digital ground to minimize crosstalk.
6	Out B	Direct output for Channel B - low-impedance (0.1 Ω), ±5 mA drive, –10 V to +0.5 V swing.
7	Sw Out B	Switched output for Channel B - multiplexed via Select switch; 250 Ω on-resistance.
8	Sw Com B	Switched common for Channel B - shared node for Sw Out B and Select switch return path.
9	Select B	TTL logic input (0.8 V max low) - controls multiplexer enabling Sw Out B onto common bus.
10	Reset B	TTL logic input (0.8 V max low) - discharges Channel B integration capacitor to analog common.
11	Hold B	TTL logic input (0.8 V max low) - disconnects input current path and freezes output voltage.
12	V–	Negative supply rail - accepts –10 V to –18 V; powers both amplifiers and switches.
13	Sw In A	Switched input for Channel A - identical function to Pin 1, mirrored for dual-channel operation.
14	In A	Direct input for Channel A - identical function to Pin 2, enabling independent signal routing.
15	Cap A	External integration capacitor connection for Channel A - same role as Pin 3, for Channel A.
16	Com A	Analog common reference for Channel A - must be isolated from digital ground per layout guidelines.
17	Gnd A	Ground return for Channel A amplifier - kept separate from Gnd B to preserve channel isolation (–80 dB).
18	Out A	Direct output for Channel A - matches Pin 6 specs; supports simultaneous dual-output readout.
19	Sw Out A	Switched output for Channel A - shares bus with Sw Out B when Select A/B are coordinated.
20	Sw Com A	Switched common for Channel A - independent of Sw Com B to prevent inter-channel coupling.
21	Select A	TTL logic input - enables Sw Out A onto multiplexed bus; timing-critical for settling (≤2 µs @ 100 pF).
22	Reset A	TTL logic input - resets Channel A independently; supports staggered integration cycles.
23	Hold A	TTL logic input - holds Channel A output while Channel B integrates, enabling interleaved sampling.
24	V+	Positive supply rail - accepts +4.5 V to +18 V; powers amplifiers, switches, and internal logic.

Key Features

Feature	Design Value
On-chip 100pF integration capacitors	Eliminates need for ultra-stable external capacitors; ±2% tolerance reduces calibration burden in production test.
Integrated Hold/Reset/Select switches	Enables fully self-contained integrate-hold-reset cycle per channel without external MOSFETs or logic.
0.1pC charge transfer error	Ensures ≤1 mV offset when using internal 100pF capacitor - critical for <12-bit precision charge measurement.
120dB dynamic range	Supports detection of 100pA–100µA currents in same system (e.g., CT scanner detector arrays with wide signal spread).
Difet® amplifier core	Delivers 100fA bias current and 10µVrms noise - outperforms bipolar op-amps in photodiode integrator applications.

Applications

Photodiode Integrator	CT Scanner Front End
Use Scenario: Converting weak, pulsed photocurrents from silicon photodiodes into stable DC voltages for digitization in optical spectroscopy systems. IC Role / Device Role / Timing Role: Dual-channel ACF2101BUG4 performs synchronous integrate-and-hold on two adjacent photodiode outputs, rejecting 50/60 Hz line noise via controlled integration windows. Use Value: 10µVrms noise floor and 0.1pC charge injection enable resolution of <100fC charge packets - sufficient for single-photon counting preamplification stages.	Use Scenario: Digitizing X-ray detector currents in computed tomography (CT) gantries where radiation dose constraints demand ultra-low-noise signal acquisition. IC Role / Device Role / Timing Role: Each ACF2101BUG4 channel conditions one detector element; Reset synchronizes to X-ray pulse, Integrate captures charge, Hold freezes output during ADC conversion. Use Value: 120dB dynamic range accommodates both low-dose scout scans and high-dose diagnostic acquisitions without gain switching or range compression.
Medical Instrumentation	Scientific Charge Measurement
Use Scenario: Measuring ion currents in mass spectrometry detectors where femtoamp-level stability and minimal droop (<1nV/µs) are mandatory over multi-second integration periods. IC Role / Device Role / Timing Role: ACF2101BUG4 operates in Integrate mode for defined time windows, then enters Hold mode to preserve signal integrity during slow serial readout of detector array. Use Value: Laser-trimmed offset (±2mV) and drift (±5µV/°C) ensure baseline stability across clinical operating temperatures (15–30°C ambient).	Use Scenario: Quantifying charge displacement in piezoelectric sensors or electrochemical cells where nanocoulomb-level accuracy is required without manual nulling. IC Role / Device Role / Timing Role: ACF2101BUG4 uses internal 100pF capacitor and Reset/Integrate sequencing to convert charge pulses into calibrated voltage steps proportional to Q = C × ΔV. Use Value: 0.5% capacitor accuracy and 0.1pC charge transfer yield absolute charge measurement uncertainty <0.6% - traceable to NIST standards.

Photodiode Integrator

CT Scanner Front End

Use Scenario: Converting weak, pulsed photocurrents from silicon photodiodes into stable DC voltages for digitization in optical spectroscopy systems.

IC Role / Device Role / Timing Role: Dual-channel ACF2101BUG4 performs synchronous integrate-and-hold on two adjacent photodiode outputs, rejecting 50/60 Hz line noise via controlled integration windows.

Use Value: 10µVrms noise floor and 0.1pC charge injection enable resolution of <100fC charge packets - sufficient for single-photon counting preamplification stages.

Use Scenario: Digitizing X-ray detector currents in computed tomography (CT) gantries where radiation dose constraints demand ultra-low-noise signal acquisition.

IC Role / Device Role / Timing Role: Each ACF2101BUG4 channel conditions one detector element; Reset synchronizes to X-ray pulse, Integrate captures charge, Hold freezes output during ADC conversion.

Use Value: 120dB dynamic range accommodates both low-dose scout scans and high-dose diagnostic acquisitions without gain switching or range compression.

Medical Instrumentation

Scientific Charge Measurement

Use Scenario: Measuring ion currents in mass spectrometry detectors where femtoamp-level stability and minimal droop (<1nV/µs) are mandatory over multi-second integration periods.

IC Role / Device Role / Timing Role: ACF2101BUG4 operates in Integrate mode for defined time windows, then enters Hold mode to preserve signal integrity during slow serial readout of detector array.

Use Value: Laser-trimmed offset (±2mV) and drift (±5µV/°C) ensure baseline stability across clinical operating temperatures (15–30°C ambient).

Use Scenario: Quantifying charge displacement in piezoelectric sensors or electrochemical cells where nanocoulomb-level accuracy is required without manual nulling.

IC Role / Device Role / Timing Role: ACF2101BUG4 uses internal 100pF capacitor and Reset/Integrate sequencing to convert charge pulses into calibrated voltage steps proportional to Q = C × ΔV.

Use Value: 0.5% capacitor accuracy and 0.1pC charge transfer yield absolute charge measurement uncertainty <0.6% - traceable to NIST standards.

Equivalent & Alternatives

The following parts are listed as comparable options for similar switched integrator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LTC1043CSW#PBF	Single-channel, ±15V only, no internal capacitor, higher 2pC charge injection, 14-bit linearity.	Requires external 100pF NP0 capacitor and additional op-amp; better suited for programmable-gain transimpedance designs.	Choose LTC1043 when needing higher voltage compliance (>±15V) or custom integration capacitance values beyond 100pF.
AD7745ARUZ	Capacitance-to-digital converter (CDC), not an integrator; 24-bit resolution, I²C interface, no analog output.	Replaces integrator+ADC chain with single-chip digital output; unsuitable for analog hold-and-multiplex architectures.	Choose AD7745 when system requires direct digital output and capacitance sensing dominates over current integration.

Compared with ACF2101BUG4, the LTC1043 offers greater supply flexibility but demands more external components and exhibits 20× higher charge injection; the AD7745 shifts architecture to digital sensing, eliminating analog signal path control entirely - making ACF2101BUG4 the only choice for precision analog integrate-hold-reset signal chains requiring dual-channel correlation.

Availability

ACF2101BUG4 is available at Aetrix Electronics and suitable for medical imaging, scientific instrumentation, and industrial CT scanner front-end designs requiring stable component supply and long-term lifecycle support.

Supply support for ACF2101BUG4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in high-precision analog ICs for test & measurement, medical, and industrial applications.

The ACF2101 product line was engineered specifically for low-noise, dual-channel charge integration in radiation detection and optical sensing - emphasizing laser-trimmed offset stability, sub-femtoamp bias current, and integrated switching logic to replace discrete integrator designs.

FAQ

What is the maximum integration time supported by the ACF2101BUG4 before droop degrades accuracy?

The ACF2101BUG4 exhibits 1 nV/µs droop in Hold mode with internal 100pF capacitor and 100fA amplifier bias current. Over a 1-second hold period, this accumulates to 1mV total drift - limiting practical integration time to ~100ms for <100µV error. For longer intervals, external low-leakage capacitors or periodic auto-zeroing are recommended. The ACF2101BUG4 datasheet specifies droop as 1–10 nV/µs depending on temperature and capacitor value.

Can the ACF2101BUG4 operate with only a single supply voltage?

No, the ACF2101BUG4 requires dual asymmetric supplies: a positive rail (+4.5V to +18V) and a negative rail (–10V to –18V). Its output swings to –10V, necessitating a negative supply for full-range operation. While +5V/–15V is the specified condition, operation at +12V/–5V violates the –10V minimum on V– and risks output clipping or undefined switch behavior. The ACF2101BUG4 is not designed for single-supply use.

How does the ACF2101BUG4 handle input current overload beyond ±100µA?

The ACF2101BUG4 specifies ±100µA input current range under normal operation. Exceeding this may cause saturation, increased charge injection, or accelerated droop. Absolute maximum rating is ±5mA, but sustained overload risks permanent offset shift due to junction heating. The device does not include internal current limiting; external series resistors or clamping diodes are required for overload protection. The ACF2101BUG4's reset recovery time increases by ~5µs under overload conditions.

Is the internal 100pF capacitor available for use in only one channel while the other uses an external capacitor?

Yes. Each channel (A and B) has independent Cap A and Cap B pins. Leaving Cap A unconnected (or tied to Com A) disables the internal capacitor for Channel A, allowing external C_EXT to dominate. Cap B can remain open to use its internal 100pF. This mixed configuration is explicitly supported in the ACF2101BUG4 datasheet Figure 1c and enables asymmetric integration time constants - e.g., fast response on Channel A, high-sensitivity on Channel B.

What is the purpose of the Sw Com A and Sw Com B pins on the ACF2101BUG4?

Sw Com A and Sw Com B serve as dedicated return paths for the switched outputs (Sw Out A and Sw Out B) when the Select switches are closed. They isolate switched output current from the main analog ground, preventing crosstalk during multiplexed bus operation. Per the ACF2101BUG4 pinout and Figure 3, these pins must be connected to analog common (not digital ground) and kept short and guarded - failure to do so increases charge injection and degrades channel separation below the specified –80 dB.

ACF2101BUG4 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 24-SOIC (0.295", 7.50mm Width)

Packaging:: Tube

Product Status:: Discontinued at Digi-Key

Amplifier Type:: Switched Integrator

Number of Circuits:: 2

Output Type:: -

Slew Rate:: 3V/µs

Gain Bandwidth Product:: 2 MHz

-3db Bandwidth:: -

Current - Input Bias:: 0.1 pA

Voltage - Input Offset:: 500 µV

Current - Supply:: 12mA (x2 Channels)

Current - Output / Channel:: 25 mA

Voltage - Supply Span (Min):: 14.5 V

Voltage - Supply Span (Max):: 36 V

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 24-SOIC

ACF2101BUG4 FAQ

1.How can I place an order for ACF2101BUG4 through Aetrix?

Please submit a Request for Quotation (RFQ) for ACF2101BUG4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for ACF2101BUG4 reliable?

The price and inventory of ACF2101BUG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ACF2101BUG4 is usually 5 days.

3.What payment methods are accepted for ACF2101BUG4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ACF2101BUG4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ACF2101BUG4?

ACF2101BUG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ACF2101BUG4 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for ACF2101BUG4?

For technical support, including ACF2101BUG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ACF2101BUG4 requirements.

6.How does Aetrix verify that ACF2101BUG4 is sourced from the original manufacturer or authorized distributors?

All ACF2101BUG4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that ACF2101BUG4 meets industry standards.

7.What is the process for return or replacement of ACF2101BUG4?

All ACF2101BUG4 units undergo pre-shipment inspection (PSI). If there is an issue with ACF2101BUG4, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The ACF2101BUG4 part is unused and in its original packaging.

Return procedure for ACF2101BUG4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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