Brooktree
| Company type | Private |
|---|---|
| Industry | Semiconductors, Computer hardware |
| Founded | 1983 |
| Founder | Henry Katzenstein |
| Defunct | 1996 |
| Fate | Acquired by Rockwell Semiconductor (later Conexant) |
| Headquarters | San Diego , United States |
| Products | Digital-to-analog converters, Video capture chips (Bt848, Bt878, Fusion 878) |
Brooktree Corporation was an American enterprise established in 1983 by Henry Katzenstein with the goal of commercializing an accelerated hardware design for digital-to-analog converters, delivering performance three to eight times superior to existing alternatives. Their innovative current-driven technique allowed significantly faster switching speeds compared to traditional voltage-based approaches. Brooktree’s videoDACs were pioneers in supporting 2K resolution monitors, becoming a standard component in workstation computers during the early 1990s. Nevertheless, the industry’s transition toward integrated driver solutions and fully digital monitor protocols eventually led to a decline in demand for these discrete chips.
Expanding beyond DAC technology, Brooktree ventured into the video capture sector with the introduction of the Bt848 chip in the early 1990s. This device transformed signals from radio frequency sources into digital data suitable for compression and storage, gaining widespread adoption in TV tuner card products from manufacturers such as Hauppauge Computer Works. The subsequent Bt878 iteration incorporated audio digitization capabilities, simplifying decoder hardware by reducing the number of required components. In 1996, Brooktree was acquired by Rockwell Semiconductor, which rebranded as Conexant () in 1998. The last Brooktree product, the Fusion 878 chip, integrated support for MPEG-2 encoding and decoding of ATSC digital video streams.
Background
Computer graphics systems represent colors for each screen pixel using numerical values stored in memory. To convert these digital values into analog signals suitable for display devices, a digital-to-analog convertor (DAC) is required. During the early 1980s, DACs were commonly implemented as custom hardware on graphics cards comprising multiple discrete components. Although color palettes ranged from 8 to 24 bits, pixel values were often stored using only 1 to 8 bits due to memory constraints. Each stored pixel value corresponded to specific RGB output levels through a "color lookup table" (LUT).
LUT chips
In 1981, Henry Sour Katzenstein from Los Angeles developed a groundbreaking approach to DAC manufacturing that overcame the speed limitations inherent in existing designs, which relied on voltage switching combined with color mapping chips and separate amplifiers. These conventional setups were limited to approximately 25 MHz operation—adequate for 640-pixel displays—but produced switching noise that interfered with power supplies and motherboard stability.
Katzenstein’s breakthrough involved a current-controlled output mechanism that blended positive and negative current sources, maintaining a constant "full on" power state and thereby eliminating switching noise. Although this architecture consumed continuous power and generated heat, it enabled much faster performance. By 1983, Katzenstein had founded Brooktree in San Diego, backed by venture capital funding to commercialize this innovation. The videoDAC was introduced in 1985 with a clock speed of 75 MHz—four times faster than competing products—supporting displays up to 2,048 pixels wide at 60 frames per second. Mass production commenced in 1988 alongside the rise of high-resolution monitors, allowing Brooktree to capture market share from competitors such as AMD, Analog Devices, and Texas Instruments. Prominent customers included Apple Computer, Sun Microsystems, Toshiba, and IBM.
Brooktree’s subsequent advancement was a RAMDAC that enabled programmable input-to-output color mapping using RAM-stored 18- or 24-bit RGB values, providing enhanced color flexibility across diverse applications. Despite initial success, improvements in semiconductor fabrication facilitated integration of LUT-DAC functionality with controller logic on single integrated circuits, reducing the need for Brooktree’s standalone chips.
Video capture
In the early 1990s, Brooktree transitioned its emphasis from the LUT sector to video capture technology, introducing the Bt848 chip. This chip became a common component in video capture cards for PCs and digital camcorders. For the European market, a version was developed that included teletext decoding capabilities. Its successor, the Bt878, incorporated audio decoding features such as FM radio reception, which minimized the number of parts needed for complete TV decoder solutions. The chip supported audio playback at 8-bit or 16-bit resolution with a sampling rate of 44,800 samples per second, delivering sound quality comparable to that of CDs.
During this timeframe, Brooktree was acquired by Rockwell, which subsequently spun off its semiconductor unit under the name Conexant. Conexant introduced the final model in this line, the Fusion 878A, which added an MPEG2 decoder to enable compatibility with ATSC digital television in addition to analog signals. To facilitate integration, the Fusion model reutilized the Bt878’s digital audio pins as inputs for ATSC signals, maintaining support for both digital video and audio streams.